Display difference between IE and Firefox

[gracexl]

We use Expression web to design our website. The display in IE is what we wanted. However, there are line missing around the pictures in Firefox. Most importantly, we created a yellow section(Camping Tents Buy one now) at the sidebar to highlight one of our navigation option. It shows currectly in IE, but loses its format(yellow section is missing, the text moved up, and jammed with the upper section) in Firefox. Any help would be greatly appreciated. Here is the website so that you can see the effect.

http://www.pinnacletents.com/

[Medyman]

The first step in cross-browser compatibility is to use valid markup. Fix the errors linked below first, it'll make troubleshoot a lot easier.

http://validator.w3.org/check?uri=http%3A//www.pinnacletents.com/
http://jigsaw.w3.org/css-validator/validator?uri=http%3A%2F%2Fwww.pinnacletents.com%2F&profile=css21&usermedium=all&warning=1&lang=en

[gracexl]

Thanks, Medyman

I am a newbie, and have been trying to fix all the errors for the past two days without much success. Are there any resources to show me how to fix them?

Your help is very much appreciated,

Grace

[gracexl]

For example, it said:
document type does not allow element "hr" here; missing one of "object", "applet", "map", "iframe", "button", "ins", "del" start-tag
<hr align="center" class="style35" style="height: 1px">

I use expression web, XHTML 1.0 Transitional. Can you shed some lights on how to fix it?

Thanks,

Grace