function checkform(form) {
	var emailfilter=/^\w+[\+\.\w-]*@([\w-]+\.)*\w+[\w-]*\.([a-z]{2,4}|\d+)$/i;
	var error=0;
	for (var x=0; form.elements[x]; x++ ) {
		if(form.elements[x].title == "verplicht") {
			if (form.elements[x].type == 'select-one'){
				if (form.elements[x].options[form.elements[x].selectedIndex].value == "") error++;
			}else if (form.elements[x].type == 'checkbox'){
				if (!form.elements[x].checked) error++;
			}else{
				if(form.elements[x].name=="email"){
					if (emailfilter.test(form.elements[x].value)==false) error++
				}else{
					if (form.elements[x].value == "") error++;
				}
			}
			if(error>0){
				alert( "U heeft het verplichte veld '" + form.elements[x].id + "' niet ingevuld." );
	        		form.elements[x].focus();
			        return false ;
			}
		}
	}        
}