Rendering is slow on both Mountain Lion and Mavericks in Safari.

Rendering is slow on both Mountain Lion (Safari 6) and Mavericks in Safari (Safari 7). Laggy to render on a Macbook Air, SSD, 4gb ram and 1.8 GHZ Core duo.

Due to the massive image in index page. 

EDIT; should have been more clear that I suspect it's the big image. That's what I deduct when browsing between the pages and none of them has that issue or image. Could be something else of course.