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How would one create a triangle container for an image (x-browser)

How would I create a DIV containing an IMG where the DIV cuts the image into a triangle, thereby displaying only part of the image though a triangle.
so..
<div>
<img src='some_image' />
</div>
Where the image is a square, but the DIV containing the image is a triangle.
http://www.script-tutorials.com/creating-kaleidoscope-using-jquery-and-css/ solves this very well except this solution is not x-browser friendly (non-ie).
http://css3pie.com/ looks interesting, however this relies on PHP.

You can't create a non-rectangular DOM element.
There are a few ways to hack it.
Firstly, there is a method of using CSS borders with varying widths on each side of the element to make it look triangular. It will still be a rectangle, but it will look like a triangle.
There's a tutorial on this here: http://www.russellheimlich.com/blog/pure-css-shapes-triangles-delicious-logo-and-hearts/
The down-side of this approach is that it is limited to creating right-angled triangles. You can join several of them together to get around this, but then you don't have a single container for your image.
An alternative hacky way of doing it would be to place rotated elements on top of the main element so that they cover the appropriate parts of the image and make it look triangular. This works in all browsers, although IE does have some very nasty syntax to do rotation, and it's quite heavy on the browser, considering that you'd only be using it to make shapes.
Another option might be to use CSS transforms. However this is only supported by a minority of up-to-date browsers, so it won't work for most users.
A better approach might be to use a proper graphics library for this, rather than trying to shoe-horn it into a <div> element.
I'd recommend using Raphael. It's a Javascript library which can draw directly into the browser using SVG (or VML for IE). It's trivial to create triangles using it and to fill them with a graphic. See the examples on the Raphael home page to get you started.

Depending on what you want the outcome to be, as far as i'm aware you cant make a triangle DIV without Transform:; However one solution would be having a div positioned inside the div in question with a PNG cutting of half the image showing only the transparent part through. Not sure if this is a viable option for you though.

Between SVG and canvas, which is better suited for manipulating/animating several images? Maybe neither and just use css3 transforms?

The 2nd part of the question is, which javascript library is better/easier to manipulate images with? I won't be actually drawing any shapes or anything. Other info: I'll be using jQuery and don't need to support all browsers, just webkit.
Edit:
More information: the current design is to layout/draw several rows/columns of images in a grid-like layout, with the image in the center being in "focus" (a little larger, with a border or something and some text next to it). The tricky thing is that we want the whole canvas of images to appear to slide/glide over to bring another random image into focus. So obviously the number of images in this grid needs to exceed what is visible in the viewport so that when the transition occurs there are always images occupying the canvas. Other than moving the images around, I won't be blurring them or otherwise modifying them. Eventually we will add user interactions like clicking/touching on a visible image to bring it to focus manually.
Let me know if this is not clear or still confusing.
I ran across scripty2 which seems like an alternative to using canvas/SVG for my purposes. I also started farting around with EaselJS last night, and it seems like this might work, but I'm wondering if it'll end up being more work/complex than just using standard HTML/CSS and a tool like Scripty2 to aid with animations and click/touch events. Just looking for any suggestions. Thanks!

The answer depends on your manipulation and animation.
If it's just translations, CSS wins for speed compared to canvas. I haven't tested, but I feel confident it easily beats SVG for the same sort of thing.
If you're going to be doing non-affine transformations or otherwise messing with the images (e.g. blurring them) you clearly want Canvas.
If you need event handlers per object, you clearly want a retained-mode drawing system like SVG or HTML+CSS. I haven't done enough CSS3 transforms to say how they compare in terms of speed to SVG, but they clearly do not have the robust transformation DOM of SVG.
This is a rather subjective question (or suite of questions) and you haven't yet given sufficient information for a clear answer to be possible.

drawing diagonals in every div of specific class?

Generally speaking - is it possible to draw with javascript two diagonal lines inside of a specific div on a website? It should basically look like a placeholder image … e.g. http://wightwildflowers.com/assets/images/placeholder.png
I'm just curious. If it's possible how would it be done?

You could add tags for each specific div with the correct size to your DOM and link the image. It will be a bit distorted.
OTO you can also try to create a canvas over each such div and draw the lines there.

there isn't a good native way to do this. the only pure javascript solution is to build a 2d array of some html element (table cells or divs or whatever) and treat them as pixels, coloring specific cells.
providing/generating an image is probably a good alternative.
the next option is using something like raphaeljs to generate browser supported vector images. this should work fairly reliably but adds a lot of weight to your page to draw two lines.

Is it reasonable to dynamically add and size the placeholder image you just showed? That might be your best bet.
You could also try working with the canvas element.

Hover effects on irregular polygons in CSS

I'm wondering how to go about marking up and coding hover effects for a map similar to this image.
When each district (or section) is moused over/touched/clicked I need to change the colour of it without affecting any other section. The boundaries on each section must be representative of the image and shouldn't be squares. The solution can't use canvas since the site I'm working on has to be usable in older browsers (I'm gutted, personally.)
Ideally I want to do this with CSS without using too much JavaScript or loads of images. Has anyone done this before?
Edit: I know people are suggesting the <area> tag, but AFAIK, it doesn't accept the :hover pseudo class.
Edit 2: I might use this: http://www.netzgesta.de/mapper/

Another self answer...
A few months ago I came across a library called Raphael JS - http://raphaeljs.com/. For those of you unfamiliar with it, it's an SVG DOM library first and foremost. If you know a thing or two about SVG, you'll know that IE doesn't support it, but it does support VML. Raphael caters for this as well. Awesome, right?
Anyway, I ended up saving the AI file for the map as an SVG file and importing the paths into a JSON block, basically doing the same thing as this code: http://raphaeljs.com/australia.html
The only issue I came across:
I wanted the map background to be transparent. Setting fill to transparent whilst allowing the section to accept mouseover worked in Firefox, but in IE, it failed. I instead opted for filling the path with white, then setting the opacity to 0.01. After that I duplicated the path and didn't fill it to create the border.

You can use HTML <area> Tag

If you use jQuery you can use the maphilight plugin. documented at http://davidlynch.org/projects/maphilight/docs/ and available from github at https://github.com/kemayo/maphilight

I see what the problem here is: making let's say a world map the usual way is quite a load. If I get it right, what you want is to have a territory map image and put hover effects making hover area match country borders exactly. SVG can be used for the map (the drawing part is already done) but the problem is how to generate HTML area map using SVG map coordinates. There's a solution (I've tried it, looks good at least with the demo provided) which translates SVG into Raphael (generates the coords) using PHP. But again you need raphael.js for that... well if you change your mind: https://github.com/atirip/svg2raphael. And if you're not familiar with Raphael it will take a time to get used to it, documentation is not so good -for me-.
Edit: I can confirm that translation from SVG->rapahel.js works but SVG files needs some tweaks. For what I see in the example SVG provided in svg2raphael the files were made with Adobe Illustrator. I've tried with SVG (plain) from Inkscape and it didn't work properly, but I could manage to fix the issues, for example:
svg2raphael won't translate Inkscape generated <path style="fill:#ff0000" ...></path> (will set fill="none"!!! so the result is invisible, but will translate correctly <path fill="#ff0000" ...></path> Seems like it will ignore everything inside style="".
svg2raphael misreads the alignments from Inkscape SVG, so you need to either move the illustration inside Inkscape or edit the SVG file with text editor and change the M value to M0,0.
svg2raphael can translate multiple svg elements, but looks at the main tag which Inkscape generates to align groups of illustrations, sometimes the whole illustration moves away from the render area and you see nothing. Hope this helps!
Edit 2: You can use Inkscape's style="" for creating CSS rules to apply to the SVG, that works great ang keeps style outside SVG/Raphael!

What are some of the best ways to plot/draw vector graphics on a HTML page?

I'm trying out some dynamic web page background generation using lines and text.
Take a look at my demo at http://74er.net/labs/lines.html (just focus on the yellow line).
It's a lame and inefficient method by literally creating a <span> element with 1 X 1 size and a yellow background with the X,Y position based on an ellispe formula.
My requirements is for the line creation are fairly simple (or rather straightforward):
must be created at client-side and not a dynamic image generated by server scripts
can be created based on a simple formula (circle, ellispe or just a straight line)
can be contained in a DOM element (e.g. DIV so that I can layer it as a background)
No HTML5 canvas technique (simply because it should be rendered on non-HTML5 compliant browsers)
Not too taxing on the browser like my current implementation
There's not need for:
really smooth curves (though that will be welcomed)
dotted/dashed (I'll like that as well if feasible)
Based on the above, I am almost certain SVG (with Raphaël) is the way to go BUT I am put off by lack of native SVG support in some browsers.
I have looked at Walter Zorns library, and it is has some excellent performance tuning algorithms built-in. So it'll be my choice if I can't find a more creative implementation.
Let me know if you need further clarification.

Morning,
i have enjoyed to work with the drawing features from the Dojo Toolkit. You can see it in action here:
Dojo drawing example
To Download Dojo visit:
Dojo Toolkit