var validateaddress=/^\w+[\+\.\w-]*@([\w-]+\.)*\w+[\w-]*\.([a-z]{2,4}|\d+)$/i

function checkmail(t){
var returnval=validateaddress.test(t.value)
if (returnval==false){
alert("Please enter a valid email address.")
t.select()
}
return returnval
}