Textbox/input text element longer than it should be

Textbox/input text element longer than it should be

So the problem is that in my div around listbox(select) + textbox(input
text) + button(input submit) I have width:250px for the whole div and for
the each thing inside it I have width:100%.
That makes me assume that they should logically fill the space inside that
div. But the problem is that the textbox(input text in the fiddle) is
kinda longer(or the other elements are shorter?).
Any ideas why and how to solve this problem?
Demo: http://jsfiddle.net/xXVHu/15/



In my whole code all the divs I have have some kind of meaning so if you
feel like they are useless, they aren't!