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Adding offset().top amount on scroll

I have a fixed piece of text and I'm trying to add a different class each time the text enters a div on scroll. I've got it working no problem. But if I add an offset amount to the fixed text e.g.
top: 400px
I need to counter this offset in the JS. But I can't seem to figure it out. I've tried using:
.offset().top 400);
But it's not working. Here's a code i'm currently using:
HTML
<p class="text">TEXT HERE</p>
<div class="section1"></div>
<div class="section2"></div>
<div class="section3"></div>
<div class="section4"></div>
JS
$(window).scroll(function (event) {
var scroll = $(window).scrollTop();
$('.text').toggleClass('blue',
scroll >= $('.section1').offset().top
);
$('.text').toggleClass('magenta',
scroll >= $('.section2').offset().top
);
$('.text').toggleClass('green',
scroll >= $('.section3').offset().top
);
$('.text').toggleClass('orange',
scroll >= $('.section4').offset().top
);
});
//trigger the scroll
$(window).scroll();//ensure if you're in current position when page is refreshed
The text needs to add class as soon as it enters the relevant div.
Here's a working fiddle: http://jsfiddle.net/6PrQW/334/

So you did most everything right, but I think where you went wrong is here: var scroll = $(window).scrollTop();
You don't want to calculate using the window offset, rather you want to use the offset of your sticky text. So instead use: var scroll = $('.text').offset().top;
Let me know if that helps.
edit,
and here is your fiddle with the edits.
Note that I edited your line for setting the blue class since you don't want to match the sticky offset against itself.

To find out when something is within your window, you've gotta use something like...
if($(elem).offset().top - $(window).scrollTop < $(window).height()){
//stuff
}
That should trigger as soon as elem is visible on the page! You can check it against $(window).height()/2, for example, if you want it to trigger in the center of the page instead. Hope this helps!

How to stick a div at the bottom of the page while scrolling after checkbox is checked

Usually I don't ask questions...I'm looking for a solution until I give up,
and this is the case here.
There are many similar questions to my but after a thorough search I found nothing.
So the question is:
After selecting a checkbox the div at the bottom of the page
shuold be sticky untill the user scrolling down to the original place where it was.
I have a great example from kickstarter web site :
If only I could know how they do it :)
If I was not clear enough I'd love to explain myself better.
Thanks in advance

After clicking on checkbox,
You can add these CSS lines to div
position:fixed;
bottom:0;

you want to add position: fixed and attach it to the bottom of the container when checked
html
<div class="wrapper">
<input type="checkbox" id="check"/>
<div id="foot"></div>
</div>
js
var check = document.getElementById('check');
var foot = document.getElementById('foot');
check.addEventListener('change', function () {
if (check.checked) {
foot.style.position = 'fixed';
foot.style.bottom = 0;
}
});
fiddle - http://jsfiddle.net/qak2ept6/
EDIT - http://jsfiddle.net/qak2ept6/1/ restore when unchecked
EDIT EDIT - http://jsfiddle.net/qak2ept6/3/ attach on scroll

when you check the check box. create div with position fixed and store the offset of the bottom edge of the window that would be normally your window height. Assign scroll event and keep checking if the scroll value is equal to the offset you have stored and when it reached just remove the fixed position from the div.

My guess (and if I was doing it) It'll be done by monitoring scroll position and applying a css style or not accordingly.
Something like
Inject it in invisible state in to the document
Note it's position (y coord)
Apply class to make it stick to the bottom of the window and show
On scroll, as soon as you get near the expected yCoord, remove the class and let it assume it's rightful place in the document
On further scroll (when you scroll away), re-apply class until you scroll back
HTH

If i have understood your question, I guess what you want is here
function sticky_relocate() {
var window_top = $(window).scrollTop();
var div_top = $('#sticky-anchor').offset().top
if (window_top > div_top) {
$('#sticky').addClass('stick');
} else {
$('#sticky').removeClass('stick');
}
}
$(function () {
$(window).scroll(sticky_relocate);
sticky_relocate();
});
If not, please explain us with more code and what exactly you need

How to make div appear from the top when scrolling down?

I would like a div to appear and slide down once you scroll pass the header.
Here's what it should look like:
http://www.space.com/11425-photos-supernovas-star-explosions.html
Here's what I got so far but it's not working.
http://jsfiddle.net/nHnrd/

You'll need to find out the height of the header and its position on the page then just show or hide the div depending on the scrollTop value using jquery.
For example:
// Get the headers position from the top of the page, plus its own height
var startY = $('header').position().top + $('header').outerHeight();
$(window).scroll(function(){
checkY();
});
function checkY(){
if( $(window).scrollTop() > startY ){
$('.fixedDiv').slideDown();
}else{
$('.fixedDiv').slideUp();
}
}
// Do this on load just in case the user starts half way down the page
checkY();
Then you'll just need to set the .fixedDiv to position:fixed: top: 0; left: 0;
Edit: I've added a checkY() function that you can call whenever the page loads as well as on scroll. To hide it initially though, just use CSS.

You might want to just show and hide your div rather than pseudo class AND hide and show
initially:
$("#mydiv").hide();
then (on scroll):
$("#mydiv").show();
set what you want your div to look like i.e. 0,0 and fixed
Use the Keep It Simple method!

I've updated your jsfiddle with something you can try.
Try this:
http://jsfiddle.net/nHnrd/10/
Also, this article was helpful:
http://www.wduffy.co.uk/blog/keep-element-in-view-while-scrolling-using-jquery/

Can you hide an html div with jQuery/Javascript when the page is scrolled to a certain number of pixels?

I have a div that is fixed position that I want hidden once the page is scrolled to a certain position. Is there any way to do this with jQuery/Javascript?

Yep, something like this should do the trick:
var max_scroll = 300;
$(document).scroll(function(){
if($(this).scrollTop() >= max_scroll)
{
$('#my_div').fadeOut();
}
});

$(document).scroll(function(){
if($(document).scrollTop()>100){
$("#myElement").hide();
}
}
edit: Oop, I see someone already posted a working solution,

Drop down interface from top of page using javascript

Quite simply, I want to know how I can do this 'http://www.lido-troon.co.uk/'.
Where it says 'Reserve a table'. This trigger allows a drop down interface to animate as if from above.
I'm not interested in the booking system in there, just the functionality.
I thought it could be done using anchors and smooth scroll, but that would mean the booking form was always there.

I will give you a code that will center this div on the top of the screen on every screen and will slide the div down from the top onLoad:
HTML:
<div id="ID_NAME">Your Content</div>
JQuery:
jQuery.fn.center = function () {
this.css("position","absolute");
this.css("top","-100px");
this.css("left", (($(window).width() - this.outerWidth()) / 2) + $(window).scrollLeft() + "px");return this;
}
$(document).ready(function(){
$('#ID_NAME').center().delay(300).animate({'top' : '0px'});
});
Hope this helped

Create the content and then show it using JQuery:
http://api.jquery.com/show/

You can have the top div with your booking system content hidden with jQuery's hide() than on .click() of the button (a tag), have it slideDown()
Example:
$(document).ready(function() {
$('booking_div').hide();
$('booking_a').click(function() {
$('booking_div').slideDown();
});
});

You can use javascript, Jquery. that have many UI effect. It's good and easy to use. You can learning it from document. e.g. http://www.webdesignersblog.net/coding/20-advanced-jquery-effects/ http://www.1stwebdesigner.com/css/38-jquery-and-css-drop-down-multi-level-menu-solutions/

Yes you can,
create div at the top of your page with the style="display: none;" or set class with the css from style attribute. Then attach event click to your link and animate change.
JavaScript
$('#your_link_button').click(function()
{
$("#container").slideToggle('slow');
});
CSS
.hidden { display: none; }
HTML
<body>
<div id="container" class="hidden">your content</div>
...