When the internet first became popular as a commercial tool anyone who could figure out how to make a website made a lot of money. At that time there weren't many sites or much competition. There was also one other thing different about that time. You could earn substantial income from selling advertising space.
Advertising space is usually sold in denominations of CPM. This is the same as 1000 views of your ad. For a while it was possible to earn $2.00 to $3.00 per CPM. So the first few sites to get high traffic simply because they had interesting content could make several thousand dollars a month without really doing anything.
Times have changed however and a CPM today only pays pennies compared to what it used to. This is an important piece of information t know if you are running a website. It basically means that trying to run a business where your sole source of income is from ads on your website is not a good idea. In fact, there are only a few websites left that can actually accomplish this and they pretty much break even. As visitors go up and ad revenue increases so do expenses for hosting. With prices today these two things pretty much cancel each other out.
Using some advertisements on your site for extra income is a good idea. Just don't think that it can be your business plan.
