You could also use negative margins instead of float, since images tend to be fixed size.... I'd have to see what it is you are trying to do both for real content and actual image but it looks to me like you're already thinking presentation before you even have your content marked up semantically... hence the presence of an IMG tag on what is quite likely NOT a content image.
Of course the wasteful and pointless HTML 5 asshattery and extra DIV for nothing probably isn't helping matters either... since you're basically using them to apply style that could just be put on the UL itself. (why I consider header, nav, content, section and all those new tags to be useless pointless idiotic rubbish setting coding practices BACK to 1998)
@stomme -- another reason I use a user.css; I'm seeing arial here.