Search engine optimization (SEO) is the process of improving the traffic to a website as a result of "organic" searches -- unpaid search results on search engines. Studies have shown that internet searchers are more likely to select websites that appear higher on the search engine results pages (typically within the first 2-3 results pages), so appearing higher up on the search results page should yield increased website traffic.

Thus, the aim of SEO activity is to cause the target website to appear higher on the target customers' search results pages.

When a searcher types words into a search engine, those words are called keywords. Keywords, as the name suggests, are the key to search engine optimization. When a web page is optimized for search, it is usually optimized for specific keywords. Thus, "baseball" and "world series" might be good keywords for a baseball website, while "Lindsey Lohan" and "Paris Hilton" would be a better keywords for a celebrity gossip website.

Clearly, a website owner needs to first determine what keywords they think their target market will be searching. Once they know the right keywords, the website can be optimized to them.

None of the major search engines -- Google, Yahoo, AOL, MSN, etc. -- publish the algorithms used to determine their search engine results. For this reason, no third-party company or consultant can guarantee they know how these algorithms work. However, trial and error and some good judgment have yielded some solid ideas about how to go about improving a website's SEO. (Your mileage may vary...)

Good SEO practices fall into three general categories: Structural, Contextual, and External.

Structural -- Many aspects of a website can help or hurt search results. Typically, these range from minor web page coding changes to major web page reconstruction, depending on the state of the website and how far the website owner is willing to go. Also, many of these changes are keyword-independent, best-practice types of changes that will work on pretty much any website.

Here are some examples (keeping in mind, again, that these are based on "solid" but circumstantial evidence):

• Web page titles are the words that display on the top window bar, next to the name of your browser. (On this page, the title is Search Engine Optimization.) Including keywords in the web page title will improve the search results for a web page.
• Metatags are data about the web page. (Titles are one example of metatags.) The choices given on search results page display two metatags -- the page title (mentioned above) and the page description. While there is disagreement over whether the description has any weight in search algorithms, it does show up on the results page and can be the reason that a searcher selects one website over another.
• Interlinking is an effective way of ensuring that search engines are aware of all the web pages on a website. If every page is accessible in two or three clicks from every other page, the search engines will take note of them. Anything beyond that will tend to be ignored by the search engine, and no amount of optimization will help a web page that the search engine doesn't know about.

There are dozens of other changes that can and should be made, but care must also be taken to avoid known problems that can penalize a website's search results. Here are two major examples of this:

• Flash-based websites are a favorite among musicians and other creative types. They can be quite stunning and innovative. However, no search engine at this time can read anything inside a Flash program. Thus, when considering SEO, using a Flash-based approach severely constrains what can be done to improve a website's search results.
• Java-based menus are another innovative but problematic technique. Search engines currently cannot read Java links and so can miss entire sections of a website.

Contextual -- In the world of websites content is king, and doubly so for search engines. Having good content will attract readers, and having good content that is rich in keywords will improve a website's search results.

Care should be taken not to try to stuff too many keywords into the content. In the past, webmasters sought to "game" the search engines by overloading their content with keywords to the extent that the content no longer made sense to read (i.e., inserting "baseball" after every third word). Search engine companies eventually caught on to these and other such "shenanigans" and seem to actually penalize websites that use them.

Avoid these shenanigans. Instead, write something worth saying that others will find worth reading. The keywords will take care of themselves, as long as you do a good job of writing. Also, break up your content visually by using bullets, bold, or italics -- this will help keep your readers from losing interest in your words.

External -- Once a website is optimized structurally and has good content, there are still things that can be done outside the site to improve its search performance.

• Link exchanges -- A good webmaster will find other websites that appeal to the same target market and seek to do a link exchange with them. Link exchanges involve each site placing a link to the other site on one of their pages. The idea here is that visitors to one website might find the other interesting and vice versa. Care should be taken when doing link exchanges, however. Links that sit on a deep web page (several clicks from the home page) along with dozens or hundreds of other links are not favored by the search engines. These are called link farms and don't help SEO efforts. Also, link exchanges should involve websites that appeal to similar markets to be relevant both from a business and SEO perspective.
• Direct Links -- Similar to link exchanges, direct links are links to your website that you can place yourself that don't require you to link back to anywhere. Many social networking sites like MySpace and Facebook allow you to place direct links back to your web site, as do other sites with semi-social aspects like Yahoo Answers.

A related activity is search engine marketing, or SEM. Similar to SEO, SEM is the process of improving the traffic to a website as a result of "paid" search results. Search engines sell preferred placement on search results pages, and SEM involves the management of this process. (An example of this is Google's Adwords program.) Paid ads will typically be shown in a shaded area above or to the right of the organic search results.

SEO and SEM are two distinctly different activities, and neither requires the other to work properly. However, consulting companies often will blur the lines between these when presenting their services to clients. It is typically easier to throw the client's money at SEM than it is to do the hard work needed to properly SEO a website.

SEM can be a good way to jumpstart a new website, and can be used effectively to take an existing website in new directions or test customer reaction to new keywords. The big difference between SEM and SEO, however, is that SEM stops being effective when you stop paying for it. SEO efforts continue to pay off well after they are completed and paid for.