Proper HTML code: Many search engines cannot properly catalog or index a site that has HTML errors. This reduces the amount of traffic your web site receives from search engines. If you want your site listed on search engines then make sure that you have correct HTML code.
Search engine: The search engine is equivalent of a version 2 browser. It cannot read flash, DHTML, JavaScript and dynamic pages even having trouble at times with frames. Search engines may have difficulty in crawling, indexing, and extracting the content of your site if you have broken HTML. The lowest form of "browser" is the search engine.
Key HTML components: The key components are titles, descriptions, visible text, alt image tags etc. If you don't find them because of typos or other mistakes, the spiders may leave them without reading the content of the page. Search engines score a page by looking for relevant terms in key HTML components of specific places within a document.
Proper document structure: Poor document structure like META tag placed in the BODY section of the page instead of the HEAD section can cause the spider to ignore the tag and cost you a good ranking.
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