Develop custom extensions for Firefox, Chrome & MSIE

I need you to create a simple browser extension that will make an Ajax call for every page that a user (that has this extension installed) visits. The extension needs to then react to the response. Please create a simple extension (Chrome, FF & IE) that will make an AJAX call to some server (yours or mine) and sends the URL of the current page to the server. The server in return may send a 'Hello World" response back with the current time. Lets just alert the current server time as a Proof-of-Concept. Thanks.