var emailfilter=/^\w+[\+\.\w-]*@([\w-]+\.)*\w+[\w-]*\.([a-z]{2,4}|\d+)$/i
 
function chk() {
var returnval=emailfilter.test(document.getcat.email.value)
if (returnval==false){
alert("Please enter a valid email address.")
document.getcat.email.select()
return false
}
}