Images not showing in Firefox

[Fionnan]

Hi all,
I'm using GetSimple now after it being recommended by a friend. Its a great CMS and does what it says on the tin!
However, I'm having one slight problem at the moment where my images aren't showing in FF but show fine in IE and chrome.
Has anyone come across this before.
You can see it on http://cotodevera.sabretoothdesign.com, its very rough at the moment but you'll see the problem on the homepage!

Thanks,
Fionnan