Minor Description
It would be nice if the DebugBar would emit valid XHTML.
In its current form, it emits img elements that lack the necessary alt attribute. This means that when you include a DebugBar on your page, it will cause XHTML validation of that page to fail.
This is a minor issue, but the fix is also very simple: just add alt attributes to the DebugBar img elements.
I will attach a patch.