var groesse = 10
function mehr() {groesse = groesse+2;
 for(var i = 0; i < document.getElementsByTagName("span").length; i++) {
   document.getElementsByTagName("span")[i].style.fontSize = groesse+"px";
   document.getElementsByTagName("span")[i].style.lineHeight = groesse+15+"px";
   }
   design();return false;
   }
   function weniger() {groesse = groesse-2;
 for(var i = 0; i < document.getElementsByTagName("span").length; i++) {
   document.getElementsByTagName("span")[i].style.fontSize = groesse+"px";
   document.getElementsByTagName("span")[i].style.lineHeight = groesse+15+"px";
   }
   usability();return false;
   }