var nowactive='';
var old='';
function active(im){
	old = nowactive;
	nowactive = im;
	document[im].src = 'img/btn/' + im + '_s.gif';
}
function flipoff(im){
	if (nowactive!=im){
		document[im].src = 'img/btn/' + im + '.gif';
	}
}
function flipon(im){
	document[im].src = 'img/btn/' + im + '_s.gif';
}

var myimg=new Array();
function preloadimg(){
	for (i=0;i<preloadimg.arguments.length;i++){
		myimg[i]=new Image();
		myimg[i].src=preloadimg.arguments[i];
	}
}
preloadimg("img/btn/welkom_s.gif", "img/btn/wie_s.gif", "img/btn/contact_s.gif");

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 ;
			}
		}
	}        
}