Month: April 2006

I use both the Safari and Firefox browsers every day. Safari is fast and approaches perfection in following human interface guidelines. Firefox has extensions.

Here are the Firefox extensions that have me hooked:

• Web Developer — lets you edit CSS, resize windows to match different screen sizes, outline any element, validate your code, look at form variables, and much more. This is a must-have for any web developer/programmer.
• ColorZilla — find out the color code for any color on the web page using this eye dropper. A must have for any web designer.
• FireBug — comprehensive error reporting and DOM controls for JavaScript. A must-have for JavaScript programmers.
• LiveHTTPHeaders — captures HTTP traffic, including SSL traffic. A must-have for screen scrapers.
• Google Toolbar for Firefox — shows Google Pagerank. A must-have for Internet marketers.
• Forecastfox — displays the weather in the status bar. A must have for motorcycle and scooter riders.

A couple of weeks ago I learned about a new technology (actually a new name for an old technology) called Comet. But I didn’t catch the parallel to Ajax — they’re both names for household cleaners (duh) — until I was talking with Phil yesterday.

The heart of AJAX is the XMLHTTPRequest object that sits in a user’s browser. This object can make its own connections to web servers, allowing content to be downloaded and refreshed on the screen based on an event in the browser. For example, if you zoom or pan a Google Map, the XMLHTTPRequest object downloads a new set of images for the map, without reloading the page.

Comet is similar, allowing content to be refreshed without reloading the page. But Comet doesn’t require an event to occur on the user’s end. Gmail’s embeddded chat is an application of Comet. The server can push content (in this case, new chat conversations) to the client at will.

The secret behind Comet is an embedded iframe through which a connection to the server remains continously open. This takes some extra tweaking of the server, but Comet connections don’t have the overhead of an Ajax model which must poll the server at some interval.

Ajax and Comet are similar but not fully interchangeable; I can see uses for each.

Read more about Comet. Also read about Comet from Phil Windley.