Search engines use complex mathematical algorithms to interpret which websites a user seeks. In this diagram, if each bubble represents a website, programs sometimes called spiders examine which sites link to which other sites, with arrows representing these links. Websites getting more inbound links, or stronger links, are presumed to be more important and what the user is searching for. In this example, since website B is the recipient of numerous inbound links, it ranks more highly in a web search. And the links "carry through", such that website C, even though it only has one inbound link, has an inbound link from a highly popular site (B) while site E does not. Note: Percentages are rounded.
To avoid undesirable content in the search indexes, webmasters can instruct spiders not to crawl certain files or directories through the standard robots.txt file in the root directory of the domain. Additionally, a page can be explicitly excluded from a search engine's database by using a meta tag specific to robots (usually ). When a search engine visits a site, the robots.txt located in the root directory is the first file crawled. The robots.txt file is then parsed and will instruct the robot as to which pages are not to be crawled. As a search engine crawler may keep a cached copy of this file, it may on occasion crawl pages a webmaster does not wish crawled. Pages typically prevented from being crawled include login specific pages such as shopping carts and user-specific content such as search results from internal searches. In March 2007, Google warned webmasters that they should prevent indexing of internal search results because those pages are considered search spam.
The first relates to internal link structure. I’ve made the mistake you say you’ve seen so often. I have a primary keyword and have used that keyword in the main navigation, linked to a page optimized for that keyword. But I’ve also got a bunch of contextual links in posts pointing to that page, usually with the keyword in the anchor text. I now understand that those internal links aren’t helping much, at least from an SEO perspective. Am I better to remove that keyword and direct link from the menu and simply link the page from multiple posts and pages within the site. Or will I get better results leaving it in the main menu and changing the contextual links in the posts to point to a related page with a different keyword?