function OpenWin(mypage,myname,w,h,features) {
     if(screen.width){
     var winl = (screen.width-w)/2;
     var wint = (screen.height-h)/2;
     }else{winl = 0;wint =0;}
     if (winl < 0) winl = 0;
     if (wint < 0) wint = 0;
     var settings = 'height=' + h + ',';
     settings += 'width=' + w + ',';
     settings += 'top=' + wint + ',';
     settings += 'left=' + winl + ',';
     settings += features;
     win = window.open(mypage,myname,settings);
//             win = window.open(mypage,myname,"");
     win.window.focus();

  }

function checkIfEmpty(field) {
	if (document.getElementById(field).value != "") {
   		return true;
	} else {
   		//alert(field + " is verplicht");
	    document.getElementById(field).focus();
	   return false;
 	}
}

function checkValidEmailAddress(obj) {
	var myEMailIsValid = true;
	var myAtSymbolAt = document.getElementById(obj).value.indexOf('@');
	var myLastDotAt = document.getElementById(obj).value.lastIndexOf('.');
	var mySpaceAt = document.getElementById(obj).value.indexOf(' ');
	var myLength = document.getElementById(obj).length;
	
	if (myAtSymbolAt < 1 ) 
	 {myEMailIsValid = false}
	
	if (myLastDotAt < myAtSymbolAt) 
	 {myEMailIsValid = false}
	
	if (myLength - myLastDotAt <= 2) 
	 {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 == true) {
		return true;
	} else {
    	//alert("email is not correct");
		//document.getElementById(obj).focus();
		return false;
	}
}