It's $500 decision time again, and I'm adding my vote to TMF Otter's call yesterday for another round of Coke. Rather than repeat the reasons for and against it here, I'll just point you to the last couple of times I wrote about it (12/29/99 and 08/25/99), Bill's column about it late last year (11/18/99), and a good article about it from Matt on (12/16/99). The Coca-Cola Company (NYSE: KO) owes its existence to advertising and now has a marketing guy at the helm instead of a finance guy. This is, in my opinion, a positive development.

With that out of the way, I'd like to spend the rest of the column on Yahoo!'s (Nasdaq: YHOO) history and infrastructure. Yahoo! is one of the oldest websites, dating back before the 1993 act of Congress that legalized commercial use of the federally funded Internet. Back then, Yahoo! was just the personal bookmarks of a couple of Stanford students -- Jerry Yang and David Filo. After it became legal to make money off of the Internet, the venture capitalist behind Netscape found them and introduced them to the concept of becoming obscenely wealthy, and the rest is history.

Yahoo! has been this portfolio's second best performer -- up more than 150% -- after little over a year of ownership. (By the way, the Fool now offers Yahoo! Research Coverage, written by our own Zeke Ashton.) A significant aspect of Yahoo!'s high-growth model is having rock-solid infrastructure in place to scale with ever-increasing usage.

So what powers the world's most popular website? Apache and Perl scripts talking to an SQL database, running on top of FreeBSD, behind some server load balancing software... with a side of French fries.

Apache is the world's most popular Web server, with a pedigree stretching back to the start of the World Wide Web. The first Web browser was invented in 1990 by a high energy physics researcher named Tim Berners-Lee at the European nuclear research laboratory CERN, who was looking for a better way to share documents with his colleagues. He posted the source code to his little project on a multimedia programming newsgroup, to see what people thought of it, and the Web took off from there.

The Web server everyone used was written and distributed (with complete source code) by the National Center for Supercomputing Applications (NSCA) here in the U.S. The NCSA Web server was the dominant Web server until 1996, but by that time all the programmers working on it had been hired away to work at a new start-up called "Netscape," and the NCSA Web server stopped being updated.

Since the NCSA Web server came with complete source code, the Web site administrators running it modified it to suit their own needs, and when new releases stopped being issued they e-mailed their modifications to each other as "patches" to the source code. Soon a man named Brian Behlendorf came up with the idea of forming a mailing list to collect all the patches and release new versions of the server with all the latest changes integrated together. They called it "a patchy server," which was soon shortened to "Apache." Today, it powers just under 60% of all Web sites.

FreeBSD is the operating system that Yahoo! runs on its servers, another Open Source version of Unix. BSD runs about 20% of the most active sites on the Web, but it doesn't get a whole lot of attention. BSD pretty much gets taken for granted because it is THE operating system that launched the Internet. In 1983, the 4.2 version of BSD included the first TCP/IP stack distributed as a basic part of an operating system. This is why the Internet was built on Unix machines.

The actual history of BSD is a great story. In practical terms, FreeBSD is to Linux about what AMD is to Intel. It's a different Unix implementation from a different group of people, but it runs the same software. It's a solid, stable, efficient, and reliable operating system that may not have all the features of Linux, but is darn good at what it does.

Perl has been referred to, affectionately, as "the duct tape of the Internet." It was created in 1987 by Larry Wall as a Swiss Army knife that gives programmers as many different ways as possible to express what they mean, so they can just sit down and write programs without having to look so much stuff up. Perl's job is to process text files, and since most of what a Web server does is spit out text files at Web browsers (which then format them prettily), Perl was a logical choice to use to make Web servers dynamically generate pages rather than just spitting out files from their hard drive. If you want to get a job as a Web techie -- and by the way, the Fool is hiring, and for more than just techies -- you'd better know Perl.

Yahoo! has dynamic content coming out its ears. For example, Yahoo! Finance attaches news stories to stock symbols by searching through the incoming news feeds for keywords, and then sticking links in to various places. It's all Perl scripts, written and maintained by a team of programmers at Yahoo!. Perl scripts stick information into databases, and Perl scripts fetch it back out and fashion it into Web pages.

There are a dozen types of SQL database software powering websites. A relational database is simply a way of storing data that sorts it as it's added so searches can be done almost instantaneously. The most popular type of brand of database software is made by Oracle (Nasdaq: ORCL), but there are plenty of others, from big corporate offerings like IBM's DB2 and Microsoft's SQL Server, to Open Source products like PostgreSQL and MySQL. Last I heard, Yahoo! was using Digital's Alta Vista database engine, but I can't tell if details about that are a company secret or if they're just very bad at communicating. It's not in their annual report or on their "About Yahoo!" Web page, and after spending a half hour on hold to tech support, the person I got didn't know. Oh well, not that important really. Whatever they're using seems to work, and if they decide to change it, they've got a dozen alternatives.

Finally, we get to load balancing software. Yahoo! has clusters of geographically distributed servers around the country to speed access. Web surfers on the East coast are talking to servers on the East coast, and a cut cable in California shouldn't knock out the whole of Yahoo!. But more than that, they have special software in their routers that tracks how busy each of their servers is and routes fresh incoming connections to the least busy server. This software also helped them defend against the recent denial-of-service attacks, when they reprogrammed it to filter out the garbage sent by the attackers to flood their system, letting them concentrate on the connections from real users.

The Motley Fool uses similar filtering software to balance the load across our own Web server farm, which you can read about here. The company providing this technology is F5 Networks (Nasdaq: FFIV), which might be worth a look as a potential Rule Breaker. F5 even uses the Fool as a customer testimonial, which is different from anecdotal evidence in that it's about a product you like, rather than one you don't like. :)

By the way, Gap (NYSE: GPS) lost ground today after reporting its same-store sales. Our Fool News team can give you the scoop.

- Oak