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("Neplatný formát e-mail adresy")
e.select()
}
return returnval
}