For Search Text Box (Execute Search Button by Pressing Enter Key)

function Fun_Search()
{
if (event.keyCode==13)
{
if(document.getElementById('search_txt').value==''||(document.getElementById('search_txt').value)=='Enter the search string')
{
alert('Search string can not be blank.');
return false;
}
document.getElementById('search_btn').disabled=true;
self.location.href='http://www.nitinkumar.com/home/search_new.aspx?find='+document.getElementById('search_txt').value;
return false;
}
}