Temporary fix for pressing Enter in IE

visibility: hidden causes IE to ignore the button, so Enter causes
nothing to submit.  This hides the button, but is ridiculous, and
dependent on the background being white on the page!  We need a real
cross-browser fix for this, so pressing Enter works across the board to
submit searches.
Moved button off screen (thanks Kurt!)
Merge pull request #86 from jegelstaff/Fix-press-Enter-search-on-IE

Temporary fix for pressing Enter in IE