Keyword Analysis and keyword density
Keywords are a very important factor on deciding your websites popularity. The Search engine spiders crawl through your website, they are merely looking to match your keywords with the search strings to decide the websites rankings. For this reason, it's very important that you have optimised your website with the most appropriate keywords to accomplish the desirable rankings in the search engines. Finding the correct Keywords is not an easy task, you should research which keywords you should use so that there closely match your websites content.
Put yourself in the shoes of the website searcher, if you were trying to find your website on a search engine, what would the keyword or key phrase you would enter in the search engine to find the products or services that your site offers? You can find tools on the internet that will assist you in choosing the best keywords for your website, Google has its own and the results are based on Google searches, this is as good place as any to start with. If your website is a web directory, your selected keyword could be “Web Directory”, but merely aiming for this particular keyword probably won’t be very effective as it is a very competitive keyword and the competition will be massive. You would be better targeting related keywords which a web directory user may type in to the search engine, for Instance “internet web directory”, “free web directory”, “paid web directory”, “web directory submit site”, these keywords are easier to target. Keyword tools will detect a large amount of related keywords, be sensible and select the keywords that describe the content of your website. As it is a very competitive keyword and the competition will be massive.
When you've selected the keywords you are trying to rank highly for, the next step is to use them within the content of your website. Having Keyword rich content increases the chances of high search engine placement. Many webmasters make the mistake of overloading the page content with the target phrases, believing that it will help with rankings, this is a mistake and some search engines will penalise your website as a result. The ideal density of keywords on a webpage, the recommended keyword density is between 3-7% for your major keywords and between 1-2% for minor ones. If you are uncertain of the density you can always use a checker, there are many available on the internet.
Keyword placement also plays a big part, if you have done your research before purchasing a domain name, you should try and include the keyword within the chosen domain name. If you are trying to rank for “Seo Directory” then get a domain name that contains it. Nowadays you can find an appropriate domain tools that will help you find a domain by entering your keywords. You should use your main keyword in your website title tags and it should also be placed in the first place of the keyword tag, Using your chosen word within <h1>, <h2> and <h3> is more than likely to give you a helping hand at ranking highly.

