Questions about making money on the Internet.

Dear habocoobschestvo, a thought arose. How do you make money on web projects?

Suppose we have a shop, there you can:
1. place an advertisement (links / banners).
2. shops offering their products can publish ads for money.
3. You can write "praiseworthy" article, it goes without saying for selfish purposes.

Who can, who knows, please share your experience, I think it will not be one to me :).

UPD incorrectly put it, not a store, but a catalog, for example, something like ozon`a or amazon`a.
')
UPD2 web store / catalog, I cited as an example, I will not give up the information and how I earn money in other web projects :)