Verify Value is Entered or Not By Javascript

 

<script type="text/javascript" language="javascript">// <![CDATA[
function validate()
{
if(document.getelementByID('t1').value.length==0)
<span> </span>{
<span> </span>alert(" username is required");
<span> </span>return false;
<span> </span>}

else {
if(document.getelementById('t2').value.length==0)

alert("password is requires");
<span> </span>return false;
<span> </span>}
alert("login successfully");
return true;

}
// ]]></script>

<form action="validation in js.php" method="post" name="frm">Enter Username <input id="t1" type="text" name="t1" /> Enter Password <input id="t2" type="password" name="t2" /> <input id="S1" type="submit" name="S1" value="Register" />onclick="return validate()"/&gt;</form>