function changeClass(i,c){
  if(document.all) 
    document.all(i).className=c;
  else if(document.getElementById)
    document.getElementById(i).className=c; 
}

function changeUrl(url){
  window.status="top =";// + top.frames.main;
  top.main.location=url;
}


function check_email_syntax(checkThisEmail){
var myEMailIsValid = true;
var myAtSymbolAt = checkThisEmail.indexOf('@');
var myLastDotAt = checkThisEmail.lastIndexOf('.');
var mySpaceAt = checkThisEmail.indexOf(' ');
var myLength = checkThisEmail.length;


// at least one @ must be present and not before position  2
// @yellow.com : NOT valid
// x@yellow.com : VALID
if (myAtSymbolAt < 1) 
 {myEMailIsValid = false;}

// at least one . (dot) afer the @ is required
// x@yellow : NOT valid
// x.y@yellow : NOT valid
// x@yellow.org : VALID
if (myLastDotAt < myAtSymbolAt) 
 {myEMailIsValid = false;}

// at least one character [nl, i, ...] must occur  after the last . (dot)
// x.y@yellow. : NOT valid
// x.y@yellow.i : VALID
// x.y@yellow.ca : VALID

if (myLength - myLastDotAt <= 1) 
 {myEMailIsValid = false;}


// no empty space " " is permitted (one may  trim the email)
// x.y@yell ow.com : NOT valid

if (mySpaceAt != -1) 
 {myEMailIsValid = false;}

if (myEMailIsValid == false) {
  alert("Het email adres dat u ingevuld heeft is niet correct");
} 

return myEMailIsValid;
}