Javascript Form Validation

<form action="<?php echo $_SERVER['PHP_SELF'];?>" method="POST" name="registration" onSubmit="return formValidation();">
<input  maxlength="255" name="name" size="30" type="text" />
<input  maxlength="255" name="emailaddress" size="30" type="text" />
<input maxlength="255" name="zipcode" size="30" type="text" />
</form>


<script type="text/javascript">
function ValidateEmail(uemail) 
{ 
var mailformat = /^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$/; 
if(uemail.value.match(mailformat)) 
{ 
return true; 
} 
else 
{ 
alert("You have entered an invalid email address!"); 
uemail.focus(); 
return false; 
} 
}
function allnumeric(uzip) 
{  
var numbers = /^[0-9]+$/; 
if(uzip.value.match(numbers)) 
{ 
return true; 
} 
else 
{ 
alert('ZIP code must have numeric characters only'); 
uzip.focus(); 
return false; 
} 
}
function formValidation() 
{ 
var name=document.registration.name;
var title=document.registration.title;
var company=document.registration.company;
var address1=document.registration.address1;
var address2=document.registration.address2;
var country=document.registration.country;
var state=document.registration.state;
var zipcode=document.registration.zipcode;
var phonenumber=document.registration.phonenumber;
var faxnumber=document.registration.faxnumber;
var emailaddress=document.registration.emailaddress;
var website=document.registration.website;
var comments=document.registration.comments;

if(name.value.length==0)
{
alert("Please enter your name");
name.focus();
return false;
}
if(company.value.length==0)
{
alert("Please enter your company");
company.focus();
return false;
}
if(address1.value.length==0)
{
alert("Please enter your Address");
address1.focus();
return false;
}
if(allnumeric(zipcode)){
if(ValidateEmail(emailaddress)) 
{
}
}
return false;
} 
</script>