Download yslow for Firefox and then you can analyse the problems on your site more clearly.
Here are some reports when I run it on your site:
Grade F on Make fewer HTTP requests
This page has 5 external stylesheets. Try combining them into one.
This page has 20 external background images. Try combining them with CSS sprites.
Decreasing the number of components on a page reduces the number of HTTP requests required to render the page, resulting in faster page loads. Some ways to reduce the number of components include: combine files, combine multiple scripts into one script, combine multiple CSS files into one style sheet, and use CSS Sprites and image maps.
js (23) 909.1K
css (6) 220.8K
iframe (3) 49.6K
cssimage (21) 225.6K
image (32) 2913.7K
favicon (1) 0.8K
xhr (2) 196.6K
redirect (1) 0.0K
You can read more details here.