Would someone like to tell me how to correct the differences on a website between ff & ie. The site is www.geturbounceon.com

I don't understand why it look different on 2 pc's running ie8 and the same on pc's running ff 3.

Is there an IE version of ff's web developer?

Also, I can't seem get that image placeholder for the zenn cart logo out from beneath the header. I have removed it from the default template folder and dealt with in the languages area, but it is still there.

Thanks