I'm developing a web application for a new service, starting from Firefox 3.5.
The interface design is tableless, only using divs + CSS & performance-blessed practices.
Now, while being compatible with Safari has taken just a small amount of time, IE is a pain.
My question is: is there anything out there that could be used to speedup cross-browser checking? I already know many points of difference between FF and IE for instance, but a specific tool would maybe help some more.
Could you suggest one, if any?
Thanks,
Scarlet
Cross Browser Development
No tool can ever make up for bad behaviour, but they can sure make life easier on you.
That being said, you should really come up with a workflow that lets you optimize for cross-browser compatability in the least amount of work spent. If that means small iterative or large monolithical steps for you, well that is up to you to decide. But generally working against several browsers during development saves you if not time at least a major headache on d-day.
List of tools/resources I find useful
Selenium is a tool for frontend
testing
IETester lets you view
a page in different IE versions
Browsershots lets you view the
page on different platforms as well
Google lets you search for known and obscure IE perversions
IE 6 No More saves you a lot of headache not bothering about the preshistorical crap that goes by the name of IE 6
YUI Graded Browser Support - make sure you know which browsers to focus on
jQuery - cross browser javascript library
YUI 3: Reset CSS - reset your CSS (link contains useful information as well as the CSS)
9 Most Common IE Bugs and How to Fix Them - very useful tips on how to get the most bang for the buck by fixing the common problems first.
Cross browser development contains lots of useful tutorials regarding cross browser development.
References
Selenium alternatives / Cross Browser Testing / Litmus
This will not answer your question, but just an advice based on my personal experience.
When you are developing for many browsers, the best thing to do is to test simultaneously on all of them while you're coding.
This way you will just have to correct small bugs each time as opposed to overwhelming complicated layout problems.
I don't know of any software that actively check for problems, but Adobe has recently released BrowserLab, which really does speed up cross-browser testing.
I would also recommend using CSS reset. This way you get a lot of inconsistencies out of the way right from the start.
I do cross-browser development and I don't really use any of the prescribed patterns, like cross-browser testing. I instead use a decorative pattern. Sometimes it works wonderfully, sometimes it's a headache, but that can be said for any development pattern.
Most of my development takes place in which browser I consider the most standards-compliant. I prefer WebKit to Presto, but both are generally neck and neck for standards compliance. With these browsers, proper use of HTML and CSS almost always leads to desirable results. My WebKit browser of choice is Google Chrome. Safari works too, but keep in mind that on Mac OS X the font smoothing tends to make text bigger. To ensure compatibility with sites designed for Safari Mac, Safari Win emboldens fonts, so it's not always the most pixel-perfect representation of your site.
Blueprint CSS can be a huge help if you're trying to quickly prototype a cross-browser site design. I'm not convinced that such a framework is always necessary, and they can also influence the way you structure your XHTML markup, and contorting your markup to match a pre-existing CSS class hierarchy isn't always a great idea.
Once I have a design that I'm happy with in my standards compliant browser, I then decorate it with bug fixes in other, less standards-compliant browsers using conditional styles or stylesheets. Firefox, at least since version 3.0, is almost never a huge issue, but there are ways of targeting Firefox specifically, and even differentiating between Gecko 1.9 and 1.8, using only CSS. It's a hack, technically, so CSS purists might scoff at the code blasphemy, but it's a reliable, usable solution. For clarity and ease of maintenance, I usually maintain my Firefox/IE fixes in isolated stylesheets and compile them with some kind of server side script, which I consider preferable to conditional include statements and JavaScript hacks. If you make use of caching with PHP, this isn't a significant bottleneck or waste of CPU time.
IETester is an indispensible tool for checking a design in all of the different IE versions, and it even uses the proper JScript engine for each release, which previous, less reliable solutions like MultipleIEs lacked.
These days, the biggest problem with cross-browser development is JavaScript, and jQuery will basically save your life here. As someone who maintained a sizable JavaScript framework for a corporate website in the days before AJAX and JavaScript interfaces, so there's no limit to the amount of praise I can give for jQuery/Prototype/Dojo.
When you say only using divs and CSS, I hope you're not absolutely positioning everything. That's a sure-fire way to mess designs up in lots of browsers. (Generally the best practice is to use floats.)
You could also try IE7.js to fix a bunch of problems with IE 6-7.
In general I'd suggest developing in IE and one of the standards-compliant browsers side-by-side (Firefox/Chrome/Safari/Opera). And try and keep both the HTML and CSS as simple as possible.
A couple more tools include
Browsera - automatic detection of cross-browser layout problems
LitmusApp - screenshots with pass/fail tagging
SuperPreview - extension to Microsoft Expression Web (currently available standalone download) where you can view an overlay screenshot of a different browser
Browserlab - extension to Adobe Dreamweaver (currently available standalone online) where you can view an overlay screenshot of a different browser
I'd also strongly recommend using a CSS reset to start such as http://meyerweb.com/eric/tools/css/reset/
Why? Because many of the cross-browser inconsistencies stem from the fact that the default style in the browser differs. For instance, a default margin may make an element layout correctly in one browser, but not the others.
It may seem weird to always be overriding default behavior, because it seems like a waste, but its absolutely necessary in order to have a baseline with which to work.
I'd recommend looking at a CSS framework like BluePrint. It has a generic way to build pages using grids, and also has some default css for forms etc.
Frameworks will have dealt with many of these cross-browser quirks during their development, so it could save you a lot of time.
Related
I need make an quick estimation on project (not sure we got):
It's an old banking CMS java web app, but the UI aimed for getting near the winform style:
Server: jdk5, weblogic 9 (JSP 1.x), only use weblogic internal servlet (not strut...).
Client: winXP, Ie6.
It was design only for use with ie6 but now we need make it also run well on new client: ie8,ie7 on win7. I understand the most difference is the client: DOM and CSS.
But my problem is we hasn't been worked with ie8, and I have not enough time to build an testing environment because our developing environment is not ready to make test (its remoting completely, and managed by another partner)
Any experience or suggestion to help me weighing this task need will be welcomed.
Edit: HTML, CSS is fairy outdated, not work on firefox at all, JS is barely procedure, no ajax, no plugins.
Client PC is limited for banking and, internal use (user not be supposed to change config or choose the browser)
Using activeX to manipulating printer and creating the report (increase ability to meet security problem )
This has nothing to do with Java, or weblogic. What you need to worry is javascript and css.
As long as your concern is limited to IE7 and IE8 only (ignoring Firefox, Chrome, etc), I think you are pretty safe. These two browsers have compatibility mode that should work with IE6 designed websites. Most problem would probably cosmetic rather than functions.
In my eyes, this is going to be impossible to tell without actually testing the application.
It'll totally depend on what kind of markup was used. Possible problems can range from near zero (if only standard markup, simple design, and basic Javascript or a framework like jQuery was used) to several weeks of fixing (heavy use of complex CSS rules optimized for IE6; heavy use of IE specific Javascript).
I'm not sure about any DOM problems since IE8 hasn't had any significant DOM updates since 1998 while any other browser is far more advanced than that. CSS and, maybe, javascript will be the big issue since you say it doesn't work in any modern browser (Firefox, Chrome, etc.)
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I am working on my first project that requires me to worry about cross browser compatibility. Since this is my first time doing so, I dont know how to go about completing the project. I am specifically worried about IE. Should I complete my project in a more graceful browser then hack it to work in IE, or should I simultaneously build my program up in both environments?
Design your site to work in standards complaint browsers first. I always start with Firefox, even when developing on my company Intranet (where everyone uses IE). Doing so will let you focus on getting your markup and CSS correct. This is what is most important.
The important thing to note is that you'll want to "future proof" your site, and concentrating on a standards compliant browser will help you do that.
Then, once you're confident your site is looking correct (validators are your friend!), try it out in the versions of IE you want to support. In order to get your layout to look OK in IE, I strongly suggest using different stylesheets for each version of IE, using conditional comments.
Also, you should note that many others have been in the same scenario as yourself, and there is quite a bit of help available. One popular method of forcing IE to behave is the ie-7.js project.
Lastly, be mindful of the top IE bugs, such as:
IE6 Box Model Bug
IE6 transparent PNG images (I have used this fix in the past)
A few tips:
Code to Standards — Start by ensuring that what you've just developed works in Firefox and Chrome, and then verify it in IE. I'll usually then check it out in Safari. It's always better to make sure your markup/code works in a more standards compliant browser first.
Validate Early, Validate Often — You don't want your design to look perfect in one browser, find out that it's broken in another, discover that to fix the broken layout you needed to correct some invalid HTML/CSS, only to find that now the first browser looks wrong.
Progressive enhancement — will be your friend. Start basic, with simple HTML and simple CSS, and no JavaScript whatsoever. Repeat tips #1 and #2, then move on to more complex styles and layout. Contiue this iterative process until you are happy with the design in all browsers. Only then should you consider JavaScript to polish the site.
Check each browser often — Don't develop the entire website in a single, compliant browser like Firefox, and then decide to "see what's broken" in IE. If you've got a complex, dynamic website, there could be MANY problems in Internet Explorer. Trying to decipher each one when they are compounding on each other is a nightmare.
Reset Stylesheet — As #Eir mentioned in the comments, find a good reset stylesheet. Although, they have fallen out of favor for some people, I find putting every browser on the same footing from the start helps tremendously.
Use a Framework — I find CSS Frameworks to be excessive, but some people swear by them, so to each his own. On the other hand, as soon as you have made it to the JavaScript phase of development, I highly recommended using jQuery or MooTools. They are very focused on circumventing cross-browser inconsistencies.
Let JSLint hurt your feelings — Even when using a JavaScript framework, there are certain standards of coding to which JSLint will help you conform. Some of the options are a bit overly strict, but I promise that if you clean your scripts through this tool often enough during development, you will almost never encounter those strange times when everything seems to work in all browsers except IE.
And some great tools! Everything in the above list you should consider mandatory practice. The following can spice it up for you in a pinch, but is optional:
CSS Browser Selector — it is rare that you will need this, but if all else fails, it's way cooler than using a separate stylesheet just for one browser (I despise conditional comments). It basically adds classes to your <html> tag, so you can do things like the following in your main stylesheet: .ie7 #header {/*stylese here for IE7 only*/}. It supports a lot of browsers on many operating systems. And it's fast.
Browsershots — Nothing beats the real thing, but if you can't install a suite of browsers, this and other tools like it can help.
IE6 CSS Fixer — I outright refuse to debug my designs in IE6. I coerced my company (via many chagrin-filled meetings with IT and management) to drop support for it (thank god). It's just counter-productive to waste so much time forcing this pile-of-ahem... Anyway, if you aren't like me and need to support IE6, this tool can help.
Also you should focus on resetting css like this
OOoooo, good question:
here's my take:
Decide which browsers you are supporting. I suggest IE 7 + 8, FF, Chrome and Safari as in order of importance. (only support IE6 if you absolutely have to!). It helps if you know your userbase here.
Use a css reset. Different browsers have different default styles. a css reset gives you a consistent base.
Keep your markup as simple as possible. Follow Standards (and see progressive enhancement on Stephen's answer).
Test every step of the way on your target browsers. That way you can correct problems right away. http://crossbrowsertesting.com/ is the best resource for this, but there are free ones for screenshots as well.
Avoid Hacks as much as possible. Most cross-browser issues these days can be solved without resorting to hacks.
Ask questions here when you get stuck. If this is your first project dealing with browsers, you will get bewildered by inconsistencies. We all face these issues, and are glad to help.
Be ok with the fact that webpages are not going to look exactly the same in all browsers. (once again, see progressive enhancement).
Good luck coding!
I develop for Firefox first, and then work out the IE buggery. Rarely do I "hack" it, rather find something that works in both, or at worst use IE conditional comments. Just one coder's preference. Always a good idea to test with Safari, too.
Two big advantages of Firefox are: the Error Console, and the Firebug plugin.
there is alot of greate tools that makes life alot easier for you there is for example a
css framework called blueprint you could use, it has already everything set for every specific browser so that you get the same outcome in all browsers. And using jquery as your javascript framework does add an extra insurance that you'll have it working in most browser.
but remeber there is no such thing as 100% cross browser compatibility for all the browsers and all the versions in world.
In theory would be best to develop for all browsers at once, always testing for every browser...
Realistically, that rarely happens... I typically develop/test with firefox. when I introduce complex javascript or css, I check in ie... this tool is incredibly handy for checking all versions at once... google ie tester.
By checking all browsers at regular intervals, and when you make complex changes, you ensure that major features are compatable :)
Also, ensuring that all of your code is valid is not only good practice, but helps identify cross browser issues.. google w3schools validator :)
Using javascript libraries such as jquery also aid in cross browser compatability, and some even come with css libraries as well. These libraries are purpose built for quick, reliable features that are typically cross browser guaranteed.
Finally, before launching, use launchlist to check that all works: http://lite.launchlist.net/
Hope all that makes sense and helps with your first project :)
what basic tips should we observe in design web pages(html/css/javascript) for having highest compatibility with most browsers(IE-firefox-opera-chrome-safari)?
thanks
Validate often and squash all validation errors by the time you make a public release. The purpose of validation, after all, is to parse the html as a standards-compliant browser would and then avoid the errors that a browser's parser would find.
Apply progressive-enhancement techniques. Often that means moving some of the complexity of dynamic pages to the back-end (e.g. php, django, what have you) so that you can have complex functionality that doesn't break in one of the thousands of different client environments in which a page's javascript will run. jQuery is excellent for narrowing the focus of your javascript development towards feature enhancement instead of open-ended features-in-javascript, and it'll help with cross-browser compatibility as well.
IE - Test in at least one live version of IE 7 or 8. Unfortunately, there really isn't any way around this, because even IE8 misbehaves like no other browser. If possible, limit your goal of support for IE6 to html/css (i.e. don't promise support for user-enhancement-features via javascript in ie6). If possible, drop support for IE 5.5 and below.
For Javascript, use libraries that are intended on being platform-independent (ie: JQuery, Prototype). Not everything will be, but it'll make your life much easier.
For CSS, I'd say follow standards, but IE tends to cause problems across the board.
Which means, you need to test, and test often. Selenium is awesome for automated functional testing, and it works with pretty much every browser. We use a Selenium RC server on a Windows machine to test IE and Firefox, which are then controlled from our standard Java JUnit tests.
Keep things simple.
The simpler your markup, CSS, and JavaScript, the easier it will be to track down incompatibilities. Try to limit yourself to CSS1 for as much as possible. Only use more modern CSS2/3 features when there is no easier way to accomplish your task.
Don't use tables, they just add extra complexity. Using semantic markup not only makes things maintainable, but also gets you the best cross browser support if done properly.
Keep in mind that floats are evil, but are also very powerful. Use them generously, but avoid trying to clear floats. Use overflow instead.
Use a JavaScript framework. Framework developers have smoothed out most of the cross-browser bugs for you. I recommend jQuery, but you can choose any framework your developers feel comfortable with. My advice is to:
Use a JavaScript framework that doesn't alter the prototypes of native objects (like Prototype JS does)
Doesn't introduce many global variables. Most frameworks follow this rule.
Aside from those 2 rules for JavaScript, try using closures to encapsulate code so you don't introduce your own global variables.
One strategy I use is to start my CSS with a set of rules that blank everything out. Each browser may have different values for element attributes so ensuring that everything is consistent from the get-go can be handy. Here is an example reset.css
http://meyerweb.com/eric/tools/css/reset/
Take a look at this great article: Browser Compatibility Tutorial
Remember: something won't just work for a specific browser (mayble a left dotted border won't show in Chrome). Do not be upset about that if you can! :) Cross-compatibility is an art that takes a lot of time.
I'm not a 100% sure if I should be posting this here but where else can I post it (definitely not Server Fault or Super User) so hopefully it's not too inappropriate.
I am currently developing a script that I hope to release as a plugin for wordpress and other open source content management systems. The script's purpose is to allow web designers to attach stylesheets and javascripts dynamically according to which browser the visitor is using. So if their site looks a little odd in Chrome for example, then they can attach a css or javascript hack just for that one browser. There will be some more features to the script as well but that is the main purpose.
Anyway, I would like to know which browsers to include support for, for that I need to know which one's gives designers/developers the most trouble. Not just the name but also the version (i.e. Internet Explorer 4). Many thanks in advance!
IE6 is by far the most problematic of all browsers. Though it's use is declining month by month, it's still widely used. All IE browsers always suffered from display issues. Sometimes margins are not what they were set to, because you need to go down the css hierarchy to set all margins for it to understand what's going on. You shouldn't need to worry about anything below IE6.
There are many articles on the Net discussing this topic.
Here's an example
All versions of IE...Microsoft never likes to conform to W3C standards so they prefer adding hacks to "conform"
I know Opera browsers don't support CSS3 yet (latest release)....Have fun!
My vote as far as problematic browsers still in prevalent use would have to be IE 6.
Whenever anyone speaks of "browser compatibility issues", in almost all cases, the real problems are with IE. Markup written to web standards generally work well in any other browser save an occasional adjustment, but there are tens if not hundreds of web sites dedicated to hacking and fixing IE while there are none dedicated to doing the same. In fact, there are already javascript libraries for this very thing, getting IE to perform like other more modern browsers, such as Dean Edwards ie7.js and 'maximize' (I think it's called).
Most developers write to standards, test in the modern browsers, adjust if necessary, then, with a shaky hand open IE. Separate CSS and javascript for modern browsers is not necessary. While some may prefer to do so with IE, most of us make do with conditional comments and feed IE what IE needs to right itself.
Most people are designing for IE6+ these days, meaning that they are designing for W3C standards with IE6 bringing up the rear guard. Here's a fantastic site that breaks down all the features browser by browser, from IE6 on up.
When coding new javascript heavy websites, which order or web browser do you code for?
I can see these possible orders, but I am not sure which I like best:
Code for one first and get it working well, then start testing with other and fix errors as I go.
This will allow for the most rapid development (with Firefox at least) but I've learned from experience that debugging IE with so much going on at once can be a pain!
Code for both at the same time. In other words, for each new feature, ensure it works with both browsers before moving on.
This seems like it will actually take more time, so maybe do several features in Firefox then move to IE to patch them up.
What do you all do?
Edit 1: To respond to a couple of answers here.:
#JQuery usage: For some reason I was not expecting this kind of a response, however, now that this seems to be the overwhelming accepted answer, I guess I should tell everyone a few more things about the specifics of my app. This is actually the DynWeb that I started another question for, and as I'm developing, a lot of the important code seems to require that I use document.whatever() instead of any JQuery or Prototype functions that I could find. Specifically, when dynamically importing changing CSS, I have to use some similar to:
var cssid = document.all ? 'rules' : 'cssRules'; //found this to take care of IE and Firefox
document.styleSheets[sheetIndex][cssid][cssRule].style[element] = value;
And I expect that I will have to continue to use this kind of raw coding currently unsupported by either JQuery or Prototype in the future. So while I would normally accept JQuery as an answer, I cannot as it is not a solution for this particular webapp.
#Wedge and bigmattyh: As the webapp is supposed to build other webapps, part of the criteria is that anything it builds look and work functionally the same in whatever browsers I support (right now I'm thinking Firefox and IE7/8 atm, maybe more later on). So as this is a more interesting (and much more complicated) problem; are there any sites, references, or insights you may have for specific trouble areas (css entities, specific javascript pitfalls and differences, etc.) and how to avoid them? I'm almost certain that I am going to have to have some sort of isIE variable and simply perform different actions based on that, but I would like to avoid it as much as possible.
Thanks for your input so far! I will keep this open for the rest of the day to see what others may have to say, and will accept an answer sometime tonight.
This is sort of a trick question. In my opinion you need to work in this order:
1: Conform to Standards
This gets you closest to working in every browser without having to test against every browser. Additionally, you gain the huge benefit that your site should work with any new browser that comes along (Chrome is a good example) so long as it's well made and standards compliant. It also makes it easier to tweak your site to work in specific browsers because the way that the popular browsers deviate from standards compliance is well known.
2: Support the Most Used Browsers (For Your Site)
Note carefully the distinction between the breakdown of browser usage on the internet vs. browser usage on your site. On the internet as a whole IE is the most popular browser with Firefox a close second and Safari, Opera, and Chrome taking up most of the remainder. However, the demographics of your site's visitors can turn these numbers upside down. On sites that cater to a more technically savvy crowd it's common for firefox to be the dominant browser with IE in the distinct minority.
3: Support Other Browsers as Needed
You need to be very explicit about the fact that browser compatibility is an operating cost for your site, and you need to decide where you draw the line. Depending on your site's purpose and business model it may be fine to support only the most popular browsers, or even a subset of them. On the other hand, it may be a vital business concern to support everything under the Sun, including IE5. It's ok to make a conscious decision to not fully support every browser if you think the cost/benefit ratio is too high to justify it. Indeed, many of the most popular sites on the internet do not work well in older and niche browsers. Though you should strive to make your site still functional in the least popular browsers, even if there are serious appearance or usability problems.
FireFox first then IE. If it works in FireFox, it is more likely to work in the other non-IE browsers, IE sometimes requires special magic.
Use jQuery and do them all at once.
Code for Firefox first, but test with IE as you go. This lets you fix any quirks as they arise. It's important to test with Firefox first because it's more standards-compliant. You should learn how to write HTML/JS the right way. Fix things as you go to get a better idea of how IE renders things differently.
You may not need to test with IE for every feature you add, but test often enough so that issues don't pile on top of each other. Repeat with other browsers/browser versions to get the overall picture of your site's compatibility.
I always test on both FireFox and IE7. And then fix and botch for IE6 and other browsers.
If it works on FireFox it will almost certainly work on Opera, Safari, Chrome, etc with only a few minor tweaks
Same thing goes for IE7 and IE6, If it works on 7 it won't take too much to get a reasonable rendering on IE6
I normally use Firefox as my main development browser because of its superior debugging tools and I code very incrementally, write a few lines and test several times an hour. But at least every hour or two I make sure that what I am doing will work on IE7 as well.
As soon as I get into an area where IE7 causes problems I start to rethink the way I'm doing it, In my experience fixes tend to multiply and get out of control very rapidly. It's often better to accept defeat and move on with a simpler design.
I've been bitten too often in the past by developing something that works perfectly on FireFox only to find that it needs a complete rethink to get it working in IE7 as well - and vice versa. It can take days to sort out and can be very disheartening.
are there any sites, references, or insights you may have for specific trouble areas (css entities, specific javascript pitfalls and differences, etc.) and how to avoid them?
A good resource for this is quirksmode. The author (Peter-Paul Koch, or PPK) has lots of compatibility tables for CSS and JavaScript support. He also has articles dealing with specific issues and how to write cross-browser code.
They don't deal with JavaScript, but Position is Everything is a valuable resource for CSS issues (mostly IE6).
Like others have mentioned, I just use jQuery to avoid these issues. If there's something it doesn't support, it's pretty easy to write custom plugins.
I do IE first, and then add Firefox.
My experience is that once it works in IE, it continues to work in IE, and the question why something not work in Firefox is usually easy to answer.
If you have to code for IE6, the most frustrating part is coding the CSS and HTML. jQuery and other libraries make it easier to code the behavior -- but you generally can't get around the fact that IE6 has so many weird rendering issues that you'll be frequently banging your head on the keys trying to make it do what Firefox, Safari and Opera do right the first time.
So Javascript isn't the hardest part. Dealing with HTML and CSS is. In my experience, if you're working with any reasonably interesting design, you're better off coding for IE first and then testing on Firefox. You probably won't have to make many adjustments if you do IE first, but you definitely will have to spend some time refitting your code to make IE do what you wanted it to, if you only code in Firefox. It's like repeating yourself. It's a pain. So it's better to get it done first so you don't end up wasting too much time.
I code for both, and write (or use) abstraction layers where there are differences between the browsers. IMHO, it's much easier in the long run to be continuously testing in a cross-platform setting. This keeps me from doing something that's tuned to one browser that simply won't work well in the other: I find out very early in the development cycle what the compatibility issues will be.
When I'm making a small change, I might first do it for one browser, but before I consider that feature or change to be complete, it must work at least in firefox and IE.
To minimize your issues now, and downstream, work with the worst to the best, in size of their existence.
Edit: If you can do the below keeping in mind of "how could this degrade gracefully down to ie6 via modified jQuery elements, etc... it might be a bit clearer.."
So, today based on Market Share, it is:
1) IE 6
2) IE 7
3) Firefox
4) Safari..etc.
Coincidentally enough, the major issues with browsers occur in that order too.
This means the majority of the issues your users will face will be in that order, and in those proportions.
On our team I have banned initial-development testing in Firefox. It has to survive the weakest link, not the strongest. Inhumane, I know, but we have cut down going back and fixing bugs related to browsers by 80%, because 80% of browser bugs are IE. Yeah, there's a ton of debugging tools in Firefox that can be used ONCE we find a problem in IE.
On the flip side we put in extra-features that are Firefox only to reward the firefox users. A simple browser type check and it takes care of the rest.
If you have look at Web Browsers market share, you will find that IE and Firefox are on the top and so close to each other so,
You should put both of them in your consideration either using cross-browser Javascritp like JQuery or go on your way by testing both of them.
I think its best to design for Firefox but like others have mentioned the JavaScript isn't the hardest part, its the CSS that is the hard part. Personally I used to code for both FF and IE at once, but I find that it takes longer because your likely to make major changes during a development cycle so don't even bother coding for both at once, it could be wasted effort.
Another thing to consider when choosing which browser to start development under is if you are more familiar with W3C standards or the IE "standard" imposed by its majority user base. Its kind of a funny thing about web standards, many if not most web developers are not happy with IE's standards support, but at the same time any code IE supports is the real standard of the web.