function checkform(f){ 
	var reEmail = /^.+\@.+\..+$/ 
	var reTel = /^(-|\+|\d|\s){9,30}$/; 
	var rePC = /^(\d\d\d\d\s?[A-Za-z][A-Za-z]|[A-Za-z]\s?\d\d\d\d)$/; 
	var reSpace=/^\s+$/; 
	var error = false;	
	
	for(var i=0;i<f.elements.length;i++){ 
          if(f.elements[i].getAttribute('mandatory')!=null && f.elements[i].type!='checkbox' && f.elements[i].type!='radio'){ 
          	   f.elements[i].style.border = '0px';
          	
               switch(f.elements[i].getAttribute('mandatory')){ 
                    case '1':  
                         if(reSpace.test(f.elements[i].value) || f.elements[i].value.length==0){ 
                         	f.elements[i].style.border = '1px solid red';
                         	error = true;
                         } 
                         break; //algemeen 
                    case '2':  
                         if(!reEmail.test(f.elements[i].value)){
                         	  f.elements[i].style.border = '1px solid red';
                              error = true;
                         } 
                         break; //email 
                    case '3':  
                         if(!rePC.test(f.elements[i].value)){ 
                         	  f.elements[i].style.border = '1px solid red';
                              error = true;
                         } 
                         break; //pc 
                    case '4':  
                         if(!reTel.test(f.elements[i].value)){ 
                         	  f.elements[i].style.border = '1px solid red';
                              error = true;
                         } 
                         break; //tel 
                    default: break;
               } 
          } 
     } 
     
     if (error) {
		 if (document.getElementById('kop')) {
		    document.getElementById('kop').innerHTML = '<div style="color: red">Vul de gemarkeerde velden in!</div>';
		 }
	    return false; 
	 }
	 else {
     	return true; 
	 }
}

function showPopup(src,width,height,feature){
	if(!width) width=800;
	if(!height) height=600;
	if(!feature || feature.length<=0) feature=',status=no,toolbar=no,scrollbars=no,menubar=no,location=no';
	var lnk=window.open(src,null,'width='+width+',height='+height+','+feature);
	lnk.focus();
}