You're gonna need to post more info than that it's something with your html or most likley your css that is causing the problem, best to post a link to the site and a description of what's up?
^ agreed. However, we can tell you this: If you're not using a doctype, use one. Make it valid and have no spaces or anything at the front (puts IE6 in quirks mode, which right there can make IE and FF different). In your CSS, try using the universal margin and padding reset. (first line of your css sheet) * { margin: 0; padding: 0; } The * means, ALL ELEMENTS. Since FF, IE, Opera, and Safari have different defaults they use for any given element, this is another possibility for causing one browsers looking different from another. After adding a proper doctype, give your code (both HTML and CSS) a check through the W3C validator. Sometimes one browsers does one thing with an error while another ignores it. Lastly, check for bugs. IE is usually the bugmaster but the others also have bugs. It's likely a bug (after you've done all the above first) is changing your layout.