my footer isn’t clearing my content and sidebar

I built my site in HTML first and got it looking right. Then I replaced the HTML and CSS of the default theme/added to it, with mine. I was pretty sure I got it right but its bugging me now cos I can’t see whats wrong. Also it looks right in IE but not FireFox. Can anyone help me?

I don’t know whether it will help to see the site, if I can post some HTML or CSS up to help please ask. Here is the site:

https://www.themortgageguide.org.uk/blog/

You may be able to see a shadow running along the bottom of the header. That is supposed to clear the content and sidebar – its the background image of the footer. Also the footer text contained within ‘footer-note’ div is positioned under the left div in FF but it should clear both left and right as it is inside the footer div.

Any ideas why the footer doesn’t clear the left and right divs when I put my html in the default theme using the theme editor? I’ve kept a lot of the original styles and replaced others – so I’m wondering if there is an original style that is causing this?