The articles you'll want to have on your site should be short enough so that someone can read them in about 5 minutes. This means you want to stick to articles of 250 to 750 words, with 300 to 600 words optimal. To give you an idea, a single page in a published novel has about 300 words.
Of course, your real purpose in putting up all these nice little short articles and changing them out frequently is not to just put information out into the world. It is to have a site that people will come back to so that they will see the Google AdSense ads, and click on them, and then you will get checks in the mail.
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