I use Atomz search to allow users to search my site and the weekly report always has the same top query. It is (drum roll please):
I have no idea why someone would search for nothing, because you get just that as a result, but search for nothing they did.
if ( document.search.sp_q.value == "" )
if ( document.search.sp_q.value.match( /^\s*$/ ) != null )
alert( "Please enter a search phrase" );
<form name="search" method="get" action="http://search.atomz.com/search/"
<input type=text size=30 name="sp_q"><br>
<input type=submit value="Search this site">