First off.. there is no such thing as PUBLIC DOMAIN. No content is yours to use freely without asking or having some kind of permission to use it. You cannot "borrow" or steal someone else's content without enormous repercussions. Don't do it. You cannot scan pictures from men's magazines and slap them on your site. It's stealing. This is a frequent Newbie mistake and pleading ignorance is not a legal excuse.
You should purchase content or sometimes you can get "free" content from a sponsor. Be sure if you purchase content that you read the contract agreement carefully. Often there are limitations on how many domains the content can be used on, if the content can be "dismembered," that is, can it be cut apart to be used for advertising, there are restrictions often on banner use or tour use, as well as other restrictions. READ the contract. It is legal and binding!
Once you have your content you should be sure to optimize it for the web. Some providers have "Web Ready" content and "Raw Content." Without getting too wordy about this, you should use the web ready content and be sure that even this is optimized. Optimizing means that the file size is small and can be quickly downloaded on a slow internet connection. Remember that most people are still using dial up connections and not broadband!
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