Using the XML HTTP Request object: "Internet Explorer on Windows, Safari on Mac OS-X and Mozilla on all platforms provide a method for client side javascript to make HTTP requests, Opera 7.6preview 1 also now features the object. This allows you to make HEAD requests to see when a resource was last modified, or to see if it even exists. It makes your scripting options more flexible allowing for POST requests without having the page change, and opens up the possibility of using PUT, DELETE etc. These methods are increasingly used to provide richer Web Applications like G-Mail that use lower bandwidth and offer snappier user response."