Main Container Firefox trouble

First suggestion: make it look good in Firefox. Ignore IE until you have the standards-compatible design working as you need it to (i.e. in Firefox, Safari, Konqueror, Opera…)

IE is a faulty browser – when you say it looks fine in IE, you’re saying you’re working backwards. It’s *very* easy to fix the IE glitches once you have the site coded to standards – but if it looks good in IE and the standards browser is off, you’re asking for mountains and valleys of migraine headaches intrying to “break” good browsers.

So, start with Firefox. Worry about IE later. Trust me.

I agree and perhaps I used the wrong wording, however can someone assist me so it works in both.

Take a look at this: WordPress Troubleshooting: I have to validate? Oh MY!!

Already checked, although there was a number of little things that needed changing there was nothing specific about the container.

‘little things’?

Well, glad it’s working for you…

The simplest way to check this:
Give all your main-divs a border (wrapper, content, sidebar etc.) – width and margin in Firefox are not the same as in IE .