Organic search (SEO): When you enter a keyword or phrase into a search engine like Google or Yahoo!, the organic results are displayed in the main body of the page.When your prospects search for information about your products and services, you want to rank highly in search engine results. By “optimizing” your site, you can improve your ranking for important search terms and phrases (“keywords”). You can also improve your rank by getting other important sites to link to yours.
Since heading tags typically make text contained in them larger than normal text on the page, this is a visual cue to users that this text is important and could help them understand something about the type of content underneath the heading text. Multiple heading sizes used in order create a hierarchical structure for your content, making it easier for users to navigate through your document.