[gb2world]

It appears your sizing guide table combined with the css you have set for the main table are causing the issue.

Look at the css for the big table with id mainframe - it is always set to be 80% of your window. As the window gets smaller - elements which cannot wrap, like your sizing guide table, are going to get to big to fit in 80% of your window next to your product image. The effect will be different in different browsers.

There are a few solutions - you may want to have your main table be a fixed width. You'll have to consider the width of the elements on your page - probably the sizing chart is the one you'll need to consider the most. If you want to keep the 80% main table - you will have to figure out how to restrict the width of your sizing table, or move it somewhere so it won't make your page so wide. (also note the width setting for your sizing chart).