function submitonce(theform){ 
//if IE 4+ or NS 6+ 
if (document.all||document.getElementById){ 
//screen thru every element in the form, and hunt down "submit" and "reset" 
for (i=0;i<theform.length;i++){ 
var tempobj=theform.elements[i] 
if(tempobj.type.toLowerCase()=="submit"||tempobj.type.toLowerCase()=="reset") 
//disable em 
tempobj.disabled=true 
} 
} 
}

// functie forum voor select cat
function nav_go(form) {
  if(form.elements['sel'].value != "") {
    location.href='?page=topics&cat='+form.elements['sel'].value;
  } else {
    // ga naar de categorie-overzichtpagina
    location.href="?page=forum";
  }
}