function ch(f,e) {

var ok=true;

var a=document.forms[f].elements[e];

var pe=a.value.indexOf('.');
var ss=a.value.indexOf(' ');
var lch=a.value.length-1;
var atr=a.value.indexOf('@');
var att=atr+1;

var sq=a.value.substring(0,atr); 
var sw=a.value.substring(atr,pe); 
var se=a.value.substring(pe,lch);

if((atr<1) || (pe<=att) || (pe==lch) || (pe<1)  || (ss != -1) || (sq.length<=2) || (sw.length<=3) || (se.length<=1)) {

alert("Please enter a valid email address.");
}
}