if (/MSIE (\d+\.\d+);/.test(navigator.userAgent)){ //test for MSIE x.x;
 var ieversion=new Number(RegExp.$1) // capture x.x portion and store as a number
 if (ieversion>=8)
  document.write("")
 else if (ieversion>=7)
  document.write("")
 else if (ieversion>=6)
  {
  alert("You are using a browser, Internet Explorer 6, which may not be fully compatible with some of the new features of this site.");
  }
 else if (ieversion>=5)
 {
  alert("You are using a browser, Internet Explorer 5, which may not be fully compatible with some of the new features of this site.");
  }
}
else
 document.write("")