Many websites, even if they are correctly designed and offer quality content, don't rank well in the search engine results. The on-page optimization consists of a set of changes and arrangements that improves the visibility of a website in the search results.
One of the funniest things that usually happens to me is that people ask me what they should do to obtain good search engine rankings once they have designed their website. My answer is really simple: redesign it.
A good and comprehensive design of a website may not give any PageRank to it but will considerably affect how a search engine evaluates it. The thing is easy: if your website sells personal computers,
you can't title you page "Bryan's world" and expect the search engines to understand it (neither your visitors). So you need to pick up a keyword/keyphrase that defines your website's content/purpose.
Once you've picked up your keywords the optimization begins. Below is a summary with a few aspects you need to cover to get a website well optimized for search engines.
The title of the page
The title of the page (the content of the "title" tag in the HTML document) is by far the most important thing when optimizing your website, and should give a short and accurate description of the page's content/purpose. Actually, that's exactly what your keywords should do, so using your keywords as the page title is definitely a good idea.
You may also include your business name in the title, but you may want to place the keywords first as they will indicate to the search engines that your page is more about your keywords than about your business name. This will be a lot better, given that your keywords will have a lot of competitors and not your business name (on most cases).
The META tags
The only two META tags that matter to us are two: the META description tag and the META keywords tag. You must fill the first with a complete but summarized description of the page, and the second with a set of comma-separated words or phrases that are closely related to the content of the page.
The importance search engines are giving to META tags these days is suspected to be very low, because formerly webmasters used to stuff these tags with nonsense text full of keywords. Anyway, it's not that hard to fill them and it's advisable to do it since it's known that META tags are used by search engines in some way.
The HTML heading elements
The HTML heading elements (, , ...) are deviced to organize the content of an HTML document. They can be used as titles, to divide and subdivide the content. This will not only help the search engines (and your visitors) understand how the content is organized on the page, but will also give more relevance to the words placed on these titles, making them a good spot for keywords.
Emphasis and strong emphasis
A good idea is to highlight your keywords all over your document. This will work even for non-robot visitors. When you highlight a word in your document, you're saying that this word is more important than the regular words.
There are two ways to emphazise your keywords: with the emphasis element () and with the strong emphasis element (). As a visual result, the emphasis element is rendered with an italic font style, and the strong emphasis is rendered with a bold font style.
URL
Search engines will check out the URL for information. This is a good reason to add keywords to your URL, which means that you have to name your HTML files and folders with keywords.
In the example previously described, you should make a folder for each category of components for sale. This will make you to URLs like "http://www.example.com/computers/notebooks/hp/dv7-2210.html", where an ordered categorization is represented, which also provides a set of keywords for the search engines.
Anchor text
Not only the text inside a page says what it's about. Also, the anchor text of a link (the content of the tag "a" in HTML) provides information about the page the link is referring to.
This is a very important point about SEO, so you should put the keywords of a page (or its variations) in every link of the website that points to that page. This will help your rankings and also your visitors, as the anchor text will give an idea of what the visitor will find after clicking the link. Never use non-descriptive anchors like "click here".
Images
You should use your keywords in the name of the image files and specially in the alternative text, also called alt text (due to the name of the "alt" attribute of the "img" tag). This will tell search engines that your image represents what your keywords describe. Most times, a correct description of the image will be perfectly related to your keywords or the page's subject.
Using these techniques in you pages will doubtlessly increase your search engine ranking for the searches you're aiming your work to. But remember that you're not building a website for the search engines only. Always try to find a balance between robots and humans, making your site both, search engine optimized and perfectly readable and comfortable for visitors.