Good Guy

It works well on my PC using FF 12. Perhaps you need to clear your cache, shut your browser and start again.

If you don’t want margins of other pages to change then you could try this code on your about page:

<div id="myabout" style="margin-left: 20px; margin-right: 20px;">

<------- Put or copy/paste your other code here ------->

</div>

The first line is self explanatory so you need to change the first line margin of 20px to whatever you want.

Good luck.