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

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