function checkEnter(e) {

var characterCode;

if(e && e.which)
{
e = e;
characterCode = e.which;
}
else
{
e = event;
characterCode = e.keyCode;
}

if(characterCode == 13)
{
__doPostBack('btnGo','');
return false; 
}
else
{
return true;
}

}