Have you seen those double underlined text inside this blog ?? They are advertising provided by Infolinks ,Kontera and other major players in In text advertising .These programs uses JavaScript to match content from a website with available advertisers in their database . Publishers are paid when user clicks on any of the advertising links generated via hover tooltip . The major advantage of in text advertising is that we don’t need any extra real estate for putting them up . They works with Adsense or any other contextual advertising network . Here is my review on both of these advertising programs .

Kontera review : Kontera is probably the major player and current market leader in text advertising .They provide a JavaScript that can be embedded easily into any website . Unlike the normal JavaScript placements , these tags are to be placed at the bottom portion of a template . So these placements really affects the page load time .
Pros : More number of advertisers and comparatively good targeting .
Widgets and auto installers for all major blogging platforms and CMSs.
Cons :Kontera really sucks when it comes to the payments . They offer support for the user to generate higher revenues but its not that working .
Payments only after 100 $ ( Via Paypal or Check ).
Statics page is not so impressive .
Join Kontera

Infolinks review : Infolinks is new entry into in text advertising . They also have the JavaScript load time issue just like Kontera and other advertising program.
Pros:Higher payments: About 2-3 time more payment than Kontera for same user traffic(US) .
Other in text advertising networks can be used along with infolinks
Cons:They currently support only very few countries and in unsupported countries , visitors are shown with a dictionary ad which not even worth a cent .
Payments only after 100$ ( Via Paypal or check )
Tooltip needs flash player .
No plugins and widgets ( Infolinks tag should be placed manually )
Less secure user login ( No SSL security )
Join Infolinks

Kontera : If you are a publisher outside US and not getting good US traffic .
Infolinks :  Inside US / outside US with good US traffic .
In text advertising programs offered by Adbrite and Clicksor are not so popular as Kontera and Infolinks . They need plenty of traffic for generating a neat sum ( In most cases its not that neat !!) .