Pls check code .html form gets submitted even if javascript returns false.
<form id="form1" name="form1" method="post" action="sub.jsp" onsubmit="return getValue()">
<input type="text" id="userName" name="userName" onkeyup="return getValue()" />
<input type="submit" name="Submit" value="Submit" />
</form>
<script type="text/javascript" >
function getValue()
{
var userName=document.getElementById("userName");
document.getElementById("userNamemsg").innerHTML="";
if(userName.value=="")
{
var mdiv=document.getElementById("userNamemsg");
mdiv.innerHTML="Error:Required Fields cannot be blank!";
form.userName.focus();
return false;
}
return true;
}