if (document.layers) { 
layerRef=".layers[";
styleRef="]";
eind = "]";
}
else if (document.all) { 
layerRef=".all[";
styleRef="].style";
eind = "]";
}
else if (document.getElementById) { 
layerRef=".getElementById(";
styleRef=").style";
eind = ")";
}
	
	function wisselt(th,blok) 
{
	eval ("document"+layerRef+"'"+th+"'"+eind+".src='images/"+blok+"'");
}