  <!--Form Validation Initiates Here. -->

 

 function validate()
 {
  if(document.frmindex.first_name.value=="")
	{
		alert("Please Enter First Name");
		document.frmindex.first_name.focus();
		return false;
		
	}
	
    if(document.frmindex.last_name.value=="")
	{
		alert("Please Enter Last Name");
		document.frmindex.last_name.focus();
		return false;
		
	}
  
  if(document.frmindex.email.value=="")
	{
		alert("Please Enter Email Address");
		document.frmindex.email.focus();
		return false;
		
	}

	if(!isValidEmailId("email"))
	{
		return false;
	}
	
	var numericExpression = /^[0-9]+$/;
  if(document.frmindex.phone.value=="")
	{
		alert("Please Enter Phone Number");
		document.frmindex.phone.focus();
		return false;
		
	}
  	 if(!document.frmindex.phone.value.match(numericExpression))
	 {
	 alert('Please Enter Numerics');
	 document.frmindex.phone.focus();
	 return false;
	 }
	 
	 if(document.frmindex.security_code.value=="")
	 {
		alert("Please enter the security code");
		return false;
	 }
  	
	 
	
 }
<!-- Form Validation Ends Here. -->