Actually, elastic website layouts are starting to dissappear... somewhat!
However, if you base your layout on percentages, you can control the width of your divisions in proportion to the overall window size, and it will adapt as the user sizes or resizes their viewing window...
This obviously can cause your site to present some very broken and chaotic layouts when the site is viewed through a non-standard window or a window that is too small (less than 800x600).
For instance, if you create a div thats 25% wide to hold your text, it's great if it's 25% of 1024px ( 256px) but what if the window is 640px (25% = 160px) or smaller... obviously, the same amount of text won't fit in a smaller space, unless of course the text changes size as well...
This can be achieved by using the 'em' unit instead of 'px' for text and margins... heres a great write-up on the matter:
Sizes In Webdesign: Em Vs. Px
Using css, it is possible to achieve a fairly liquid design that expands and contracts AND resizes fonts with the size of the window, however, special care has to be taken with images, and the effectiveness of background images becomes limited. Remember all but the most basic layouts will have a breaking point.
Here is a good general description in simple terms for those who care:
Liquid Design - A Step Forward To Make Your Website Accessible - Accessible Web Design
As for creating a site based on a liquid layout, here are some good starting points:
Liquid Designs
What is Liquid Design? [Design Practice]
here's a gem:
Create a simple liquid layout - .net magazine
If you encounter any specific questions, i'll be happy to help where I can.
Mike.