How Google Works
Updating Your Site Improves Your Visibility
Google’s mission statement is to “organize all the world’s information and make it universally accessible and useful.” As a search engine, Google’s job is to read the entire web, receive a request from you, and then decide which single page across the pool of the fifteen billion best matches your search. This is a tough job, and Google can only do as good a job as we (those in control of website content) do.
There are two basic parts to the search engine, the bot and the indexer, and they have a bee and hive sort of relationship. The bot is the bee, and it spends all its time reading the internet. It makes no decisions, but simply trolls the internet and collects information. The bot then feeds the indexer (the hive) all the data it has gathered, and the indexer then decides which results should be shown for which searches.
The first step in SEO is ensuring that the bot is interested in reading your site. Since the bot is responsible for reading the internet, it has to make decisions as to where its time is best spent. If you put a new site live today, and the bot indexes it tomorrow, then again in a week, then in three weeks, and then six, and if, each time it visits, it sees that your site has not changed, it will begin to visit your site less frequently.