While working with SEO, you should use the heading tags like h1, h2 for your keywords is extremely important. Normally you would put your keywords and <h1> important keywords here </ h1>, do you notify Google, Yahoo, Bing ... that this is your critical keywords. With the tag is less important than one bit, you can put in the h2 tag, h3 ... Header tags are sorted by descending order of importance, that is h1 is the most important, followed by h2, h3, h4, h5 and h6. In terms of web design, you should let h1 largest font size, eg 19pt, h2 is smaller than 1 bit, for example 16pt, h3 is smaller than 1 bit, for example 16pt ... Note: You should not overdo the h1 tag, even though h1 header tag is the most important. You should arrange the website content, your header so that the most reasonable, DO NOT use the entire h1 before. You also do not expect too into the tank by adding more h1 your content, although the addition of h1, h2, h3 ... will increase your score in the process of doing SEO. You always remember that you are building the content for Google, Yahoo, Bing but you are building content for the reader. Imagine that, you do a good SEO, the search results that you are in the number one position of Google, but the content for the reader, was extremely unloading and bored, the reader is available in the website of you? The answer is NO, do not you. Do good SEO, good results is one thing, but users in your website long or not is another matter.