Search engines are limited in how they crawl the web and interpret content. A webpage doesn't always look the same to you and me as it looks to a search engine. In this section, we'll focus on specific technical aspects of building (or modifying) web pages so they are structured for both search engines and human visitors alike. Share this part of the guide with your programmers, information architects, and designers, so that all parties involved in a site's construction are on the same page.
To perform better in search engine listings, your most important content should be in HTML text format. Images, Flash files, Java applets, and other non-text content are often ignored or devalued by search engine crawlers, despite advances in crawling technology. The easiest way to ensure that the words and phrases you display to your visitors are visible to search engines is to place them in the HTML text on the page.
Crawlable Link Structures
Just as search engines need to see content in order to list pages in their massive keyword-based indexes, they also need to see links in order to find the content in the first place. A crawlable link structure—one that lets the crawlers browse the pathways of a website—is vital to them finding all of the pages on a website. Hundreds of thousands of sites make the critical mistake of structuring their navigation in ways that search engines cannot access, hindering their ability to get pages listed in the search engines' indexes.
Keyword Usage and Targeting
Keywords are fundamental to the search process. They are the building blocks of language and of search. In fact, the entire science of information retrieval (including web-based search engines like Google) is based on keywords. As the engines crawl and index the contents of pages around the web, they keep track of those pages in keyword-based indexes rather than storing 25 billion web pages all in one database. Millions and millions of smaller databases, each centered on a particular keyword term or phrase, allow the engines to retrieve the data they need in a mere fraction of a second.
Obviously, if you want your page to have a chance of ranking in the search results for "dog," it's wise to make sure the word "dog" is part of the crawlable content of your document.