Keyword weight indicates significance of the keyword mentioned in a page. There are a lot of factors that affect the keyword weight. Search engines take into account the presence of the keyword in the title and tags, calculates the percentage of the keyword in the text of the page, evaluates bold and italic tags, etc.
When evaluating keyword weight, we also consider website internal factors: the presence of the keyword in meta tags (Description and Keywords tags) and in H1, H2 and H3 Heading tags. We analyze document structure, used technologies and Internal linking.