Advero.net is a free link exchange. Webmasters define their advertisements as html snippets and they will be shown on other participating sites. As it is an exchange webmasters also define spots in their own sites where other sites' advertisements will be displayed. The system tries to keep balance - your link is shown as many times as you showed others links.
Advertisement network in action:
To define the place where others advertisements will appear on your site in its html source paste this snippet:
You must edit the width and height parameters in accordance with the size of the advertisement spot on your website. Valid combinations of width and height are 300x250, 336x280, 728x90, 160x600, 468x60, 234x60, 120x600, 120x240, 250x250, 200x200, 180x150, 125x125, 728x15, 468x15, 200x90, 180x90, 160x90, 120x90.
After placing this snippet, your site should begin to display ads as long as they are available for the specified width and height.
When your page is loaded in a visitors browser advero shows an advert and your site gets one credit point. Once you place the code, your site starts to accumulate points. These points show how many impressions others sites owe you.
To spend your points you must register and define your ads.