Set Class From Javascript

//change the tab class style 
var browser=navigator.appName;
var classtyp;
 if(browser=='Microsoft Internet Explorer')
  {
    classtyp = "className";             
  }
 else
  {
     classtyp = "class";               
   }
   
if (val=='new')
  {
     document.getElementById("liUpcoming").setAttribute(classtyp, "selectednews");
     document.getElementById("liPast").setAttribute(classtyp, "");
  }