Site only works in chrome and safari?

Hello all - I just want to say I’m new to PHP/MYSQL so the problem I’m encountering may or may not be a quick simple fix. A little bit of background :

I’m using EASYPHP (Apache, MySQL, myphpadmin, and php5) to develop a site locally. I’m using an open source template which is free to use and distribute etc. Before I did the major editing and implementation of PHP, it worked on all of my browsers (Firefox, IE, Chrome, and Safari for windows)

I’ve been testing on chrome during development and I did some css stuff that I wanted to make sure worked on all the browsers. I opened it up IE and firefox, and it doesn’t work! Yet it works on chrome and safari. I wouldn’t be too confused if it was a couple of css or coding problems, but in IE and FF the only thing that loads is the background image - and nothing else. Can someone at least point me in the right direction of where I should be looking? Anyone experienced anything similar or know what may be going on?

Thank you for your time.