I got this tip from one of the HTML gurus at work and it has an amazing impact on client side performance - I mean, the difference is completely noticable, I would say 200% increase in page rendering.
The more tables you do this to in X-Cart, the better it will perform because it uses so many nested tables. Remember though, the performance increase is solely client-side, there are no server-side performance implications here...
Here is a Microsoft web page example of the effects of this. After the test page loads hit refresh a couple of times to watch the dramatic effects.
You can do this to any table where you can define the column widths! I did it in my home.tpl, product.tpl and products.tpl.
In the <table> tag you add:
style="table-layout:fixed;"
Just below the <table> tag but before any <tr> tags you add:
If you use pixles: <col width="##px">
If you use percent: <col width="##%">
Add a <col> tag for each column in the table.
There is more you can do, too but this in itself is a dramatic increase in client side performance! (You can add "width=###" to the COL tags for more performance.)
The reason this increases performance in the browser is because the browser doesn't wait for the table/cell contents before rendering the table - it renders the table immediately based on the <COL> tags instead.
I hope this helps out everyone!
--al ponte