I've recently managed to get my links on my site working so they display content in a div on the same page. I've just discovered that the content that appears is formatted in Firefox and Netscape, but in Explorer that text is just default black times new roman 12.

This is the link! (Click on home.)

Anyone have any idea why this would be happening? I was also wondering whether I should create and attach a CSS file to the content page, maybe that will make a difference??

You are going to have to add at least a link to the CSS file in the content being called into your iframe.

You've also got a lot of errors, incorrectly nested tables, and other things going on there. Validate your code.