If you missed this article (in french) on bioinfo-fr, I will just explain the code, it could be of some help.

Bookmarklets , one click tools, are little scripts stored as URL in a bookmark, or as an hyperlink in a web page. Coded in JavaScript, they add new functionalities, and can even call more complex scripts, stored somewhere else.

The code here is very simple :

javascript: The language used for writing the bookmarklet.

function() Call an anonymous function in JavaScript.

location.hostname=location.hostname+'.urlproxy'; The interesting part : It adds at the end of the domain name (location.hostname) the proxy’s URL, which automatically change the URL of the page on which you activate the bookmarklet.

If you get a 404 error. It means that the proxy was not planned for the visited site. Which could happen if you click twice on the bookmarklet.