Div not expanding to 100% (default behaviour)

[sikisajko]

I have a strange problem....Div should expand to 100% of available space by default, but its not the case.I don't understand what's going on, even if I put display:block it's behaving as automatic width (relative to content).I appreciate any help.Thanks in advance.http://jsfiddle.net/T3arP/The effect I need to achieve is let the box with green border absoluted or fixed to top of its container, so you can scroll keywords but title will remain there.