IF语句+ jQuery弹出窗口？

How would i go about having my site know lets say "IE User Visit's" and my site goes oh there on IE pop up lightbox or something. needs to support html. but say there on Mozilla or safari base browsers it just goes it because radius is supported by them

Using jQuery you could do something like this. (Not saying you should, but you could).

$(function() {
  if ($.browser.msie) {

    // You could insert your favorite lightbox script here.
    alert("You're using IE");
  }
});

As jessegavin already mentioned, this isn't recommended. That said, the following javascript condition will check to see if the browser's user agent is described as 'msie.'

if ( navigator.userAgent.toLowerCase().indexOf("msie") > -1) {
    $('#IEmessage').modal(); //or whatever 
}