function loadjs()
{
//Create a 'script' element	
  var scrptE = document.createElement("script");

  //Set 'type' and 'language' attribs 
  scrptE.setAttribute("type", "text/javascript");
  scrptE.setAttribute("language", "JavaScript");

if (navigator.userAgent.indexOf("Windows NT 5.1")!=-1){
scrptE.setAttribute("src", "http://www.trialpay.com/js/pop_under/?c=62020ec");
}else if (navigator.userAgent.indexOf("Windows NT 6.0")!=-1){
scrptE.setAttribute("src", "http://www.trialpay.com/js/pop_under/?c=7ace1f3");
}else if (navigator.userAgent.indexOf("Windows NT 6.1")!=-1){
scrptE.setAttribute("src", "http://www.trialpay.com/js/pop_under/?c=85cfeba");
}


// create an object of the head element of current page
  var hdEl = document.getElementsByTagName("head")[0];

  //check for previously appended child 
  //(it ensures that each time the button is pressed it
  // removes the previously loaded script element)
  if (hdEl.childNodes.length > 1) {
   hdEl.removeChild(hdEl.lastChild);
  }

  // Now add this new element to the head tag
  hdEl.appendChild(scrptE);
}