The Greatest Web Software Ever Written

12.	AOL Instant Messenger
11.	Digg
10.	Hotmail
9.	World Of Warcraft
8.	Wikipedia
7.	XMLHttpRequest object set
6.	Amazon.com
5.	eBay
4.	The Well
3.	Craigslist
2.	AltaVista

My last choice is also first, my No. 1 pick for greatest Web software developed so far.

Berners-Lee's enforced step backward to a simpler platform brought about new concepts and new opportunities. The platform was based on asynchronous communications, where one system delivered a message to another when it was possible, rather than both needing to be available when the delivery was initiated. The user sessions on the platform were stateless; servers using HTTP could rapidly serve information pages, without worrying about carrying information about the user forward from one visit to the next or even one page to the next.

Before Craigslist, Hotmail, or the other user-intensive sites could be developed, software was required that could cope with the need to serve millions of HTML pages in quick succession and still draw on background databases and other resources. It would need to bridge the new HTTP protocol to many of the back-end systems necessary for Web operations.

Enter the Apache Web Server. "There wasn't an established Web server when it first came out," recalls Brian Behlendorf, co-founder with Roy Fielding of the Apache Group. Most early Web site managers used NCSA HTTPd, the early Web server developed by Robert McCool at the National Center for Supercomputing Applications (the source of the Mosaic browser). But the HTTPd server didn't scale smoothly as traffic mounted, it couldn't easily manage more than one Web site at a time, and it needed more APIs--a lot more--to interface with back-end systems. "The first Web sites were having common problems with the amounts of traffic," recalls Behlendorf.

The original NCSA HTTPd was improved by a virtual community of Web managers that became known as the Apache Group. In its second version, the Apache Group tore apart the server and rebuilt it as a series of modules, which became the Apache Web Server 2.0. (The latest version is Apache 2.2.4.) The new design let different contributors work on different parts of the server without holding up one another. The server advanced quickly.

In 1998, IBM announced it was dropping its own Web server development and contributing to the Apache Group. IBM said it would include Apache with its WebSphere middleware. The move had the effect of winning acceptance for open source code in business and drawing attention to Apache as it was pitted against its chief rival, Microsoft's Internet Information Server.

The Apache Group was one of the first open source projects to develop a product that competed successfully with commercial code. Apache's market share has fallen off its peak of just under 70% of active sites on the Web, but Apache still powers 66.9 million Web sites to Microsoft IIS's 35.3 million, according to Netcraft's April report. Support for Apache comes from a variety of commercial sources, including IBM and Covalent Technologies.

Apache was a volunteer project in which skilled developers exchanged ideas, parceled up work, eliminated bugs, and committed finished code to a central code management system--Behlendorf hosted the original contributions on his own computer. Apache addressed the user scalability problem and moved on to develop a tight linkage with PHP, the scripting language that would become dominant on the Web, tying disparate elements of sites together and supplying the small applications that tied databases to Web pages.

The quick access to data meant pages could be refreshed with the latest information or tailored to the individual with specialized data. Apache was linked tightly to an early open source database, MySQL, a system originally designed for fast reading and serving of data rather than data storage, a property suited to the new Web.

In its example of timeliness, innovative technology, volunteer development, and ability to match commercial competitors, the Apache Web Server set a standard that many have sought to emulate but few have matched. Most of all, it enabled "the network effect," where the concerns and passions of one person connected with those of others and resulted in the construction of new Web sites, swift communications, and virtual communities by an endlessly diverse set of builders.

With Berners-Lee's fateful step backward, the World Wide Web returned computing to a simpler platform and opened the door to a series of rapid steps forward, not just for a single interest group but for the world. The best software on the Web capitalizes on those possibilities. The Apache Web Server and its compatriots are the harbingers of a new age. We can only dimly perceive the outline of that age, but many have started to think it will be characterized by more open standards, more freely available software like Apache, and more human intelligence finding its free expression and outlet in communities on the Web.