There are several factors that come into play when choosing a website topic. Firstly, here is a rule of thumb that I live by, always develop content that you are passionate about or interested in. When you develop a site based on content that you have no interest in it is easily recognized. The only exception to this rule is if your are creating a site for a client. In this case you have display professional composure.
One problem alot of new developers have is not keeping their site consistent with their relevant topic. If for instance I search on google "how to download iphone apps" and I click on a blog and halfway through the post the editor starts talking about a new video game coming out I will be less likely to continue reading. This new generation of technology savvy individuals have very little patience when surfing the web. Always be consistent with your main topic. Survival is key. Using google's keyword tool is great to a certain extent. However, I never base a whole site project entirely from keywords, you will most certainly fail.
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