function setlanguage(str){
   var ls = location.search;
      if(ls==''){ls='?cat='};
   var index=ls.indexOf("lang");
      if (index==-1){
	             switch(str)
				 {
				 case 'nl':location.search=ls+"&lang=nl"; break;
				 case 'fr':location.search=ls+"&lang=fr"; break;
				 case 'en':location.search=ls+"&lang=en"; break;
				 case 'du':location.search=ls+"&lang=du"; break;				 
				 }
	             
			}else{
			//alert(index+2)
			//at is de taal die momenteel in de url zit
			var at = ls.charAt(index+5)+ls.charAt(index+6);
			
			//alert (at)
			  switch(str)
				 {
				 case 'nl':location.search=ls.replace("="+at,"=nl"); break;
				 case 'fr':location.search=ls.replace("="+at,"=fr"); break;
				 case 'en':location.search=ls.replace("="+at,"=en"); break;
				 case 'du':location.search=ls.replace("="+at,"=du"); break;				 
				 }
			
            }
   }