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At first search engines were guided by the webmasters themselves. Early versions of search algorithms relied on webmaster-provided information such as category and keyword meta tags, or index files in engines like ALIWEB. Meta-tags provided a guide to each page's content. When some webmasters began to abuse meta tags, causing their pages to rank for irrelevant searches, search engines abandoned their consideration of meta tags and instead developed more complex ranking algorithms, taking into account factors that elevated a limited number of words (anti-dictionary) and were more diverse, including:
• Text within the title tag
• Domain name
• URL directories and file names
• HTML tags: headings, emphasized, strong emphasized
• Keyword proximity
• Keyword adjacency
• Keyword sequence
• Alt attributes for images
• Text within NOFRAMES tags
• Content development
• Term frequency, both in the document and globally, often misunderstood and mistakenly referred to as Keyword density