function positionFooter() {
   var heightContent = 0;
   var docHeight = 0;
   var footOffset = 225; 
   // Get biggest column height by checking left, middle and right column
   if (document.getElementById('column1')) {
      heightContent = document.getElementById('column1').offsetHeight;
   }
   if (document.getElementById('column2')) {
      heightContent = document.getElementById('column2').offsetHeight > heightContent ? document.getElementById('column2').offsetHeight : heightContent;
   }
   if (document.getElementById('column3')) {
      heightContent = document.getElementById('column3').offsetHeight > heightContent ? document.getElementById('column3').offsetHeight : heightContent;
   }
   if (document.getElementById('column4')) {
      heightContent = document.getElementById('column4').offsetHeight > heightContent ? document.getElementById('column4').offsetHeight : heightContent;
   }
   // find id "footer"
   if (document.getElementById('footer')) {
      // browser detect
      if (navigator.userAgent && navigator.userAgent.indexOf("MSIE") >= 0) {
         docHeight = document.body.clientHeight-footOffset; //pc/mac ie
      } else {
         docHeight = this.innerHeight - footOffset; //moz & saf
      }
      // alert("docHeight: " + docHeight + "\n" + "heightContent: " + heightContent);
      if (docHeight >= heightContent) {
         if (navigator.userAgent && navigator.platform.indexOf("Win32") >= 0 && navigator.userAgent.indexOf("MSIE") >= 0) {
            document.getElementById('footer').style.setAttribute('top', docHeight + 'px'); //pc ie
         } else {
            document.getElementById('footer').style.setProperty('top', docHeight + 'px', null); //moz, saf, mac ie
         }
      } else {
         if (navigator.userAgent && navigator.platform.indexOf("Win32") >= 0 && navigator.userAgent.indexOf("MSIE") >= 0) {
            document.getElementById('footer').style.setAttribute('top', heightContent + 'px');
         } else {
            document.getElementById('footer').style.setProperty('top', heightContent + 'px', null);
         }
      }
   }
}