function emailCheck(emailStr) {

 var emailPat=/^(.+)@(.+)$/;
 var specialChars="\\(\\)<>@,;:\\\\\\\"\\.\\[\\]";
 var validChars="\[^\\s" + specialChars + "\]";
 var quotedUser="(\"[^\"]*\")";
 var ipDomainPat=/^\[(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})\]$/;
 var atom=validChars + '+';
 var word="(" + atom + "|" + quotedUser + ")";
 var userPat=new RegExp("^" + word + "(\\." + word + ")*$");
 var domainPat=new RegExp("^" + atom + "(\\." + atom +")*$");
 var matchArray=emailStr.match(emailPat);
 if (matchArray==null) return false;

 var user=matchArray[1], domain=matchArray[2];

 if (user.match(userPat)==null) return false;

 var IPArray=domain.match(ipDomainPat);
 if (IPArray!=null)  {
	for (var i=1;i<=4;i++) if (IPArray[i]>255) return false     
 	return true
 }

 var domainArray=domain.match(domainPat);
 var atomPat=new RegExp(atom,"g");
 var domArr=domain.match(atomPat);
 var len=domArr.length;
 if (domArr[domArr.length-1].length<2 || domArr[domArr.length-1].length>3) return false;
 if (len<2) return false;
 return true;
}

function valida1(form) {
 if (!emailCheck(form.email.value)) {
	alert("La dirección de correo NO es correcta - E-Mail address is NOT ok");
	form.conti.disabled=false;
	return false;
 } 
 if (form.nombre.value=='') {
	alert("Debe introducir el campo NOMBRE - You must enter a NAME");
	form.conti.disabled=false;
	return false;
 }
 form.op.value='2';
 form.submit();
}

function valida2(form) {
 if (!emailCheck(form.email.value)) {
	alert("La dirección de correo NO es correcta - The E-mail address is NOT ok");
	return false;
 }
 if (form.clave2.value == '') {
	alert("Debe introducir su CLAVE - You must enter the PASSWORD"); 
	return false;
 }
 form.op.value='4';
 form.submit();
}