//ham java chinh
//-------------------------------------------------------
<script language=javascript>
		function test() {
if(document.f1.tenkh.value=="")
		{	
		alert("B?n Ph?i Nh?p Tên Khách Hàng??");
			window.document.f1.tenkh.focus();
			return false;
			}	
			else
if(document.f1.dckh.value=="")
		{	
		alert("B?n Ph?i Nh?p Ð?a Ch???");
			window.document.f1.dckh.focus();
			return false;
			}	
			else
if(document.f1.dtkh.value=="")
		{	
		alert("B?n Ph?i Nh?p S? Ði?n Tho?i Khách Hàng??");
			window.document.f1.dtkh.focus();
			return false;
			}	
			else
  if ( isNaN(window.document.f1.dtkh.value) == true) 
{ alert("Ði?n Tho?i Ph?i Là S?" );
window.document.f1.dtkh.focus();
return false; }
else
window.document.f1.submit();
}

</script>
//-------------------------------------------------------------------

//Html goi ham chay
//-------------------------------------------------------------------
<input type="button" name="Button" onclick="test();" value="Nh?p Li?u" />
//goi ham tu nut nhan Submit