function ClickReturn () {
  var bAgent = window.navigator.userAgent;
  var bAppName = window.navigator.appName;
  if ((bAppName.indexOf("Explorer") >= 0)
      && (bAgent.indexOf("Mozilla/3") >= 0)
      && (bAgent.indexOf("Mac") >= 0))
    return true; /* dont follow link */
  else return false; /* dont follow link */
}

function GotoLink(link, frame) {
  if (frame.length) {
    var hasFrame=false;
    for(i=0;i<parent.frames.length;i++) {
      if (parent.frames[i].name==frame) {
        hasFrame=true;
        break;
      }
    }
    if (hasFrame==true)
      parent.frames[frame].location = link;
    else
      window.open (link,frame,"");
  }
  else
    location = link;
  return ClickReturn();
}

function GotoXVali() {
  return GotoLink('http://validator.w3.org/check/referer', '_blank');
}

function GotoCVali() {
  return GotoLink('http://jigsaw.w3.org/css-validator/validator?uri=http://www.medizintechnik-rostock.de/src/base.css', '_blank')
}