Contextual advertising programs are the best resources for making money online. The advertisements are provided to web publishers (bloggers and site owners) by ad networks. The ad network acts as a bridge between advertiser and publisher. The advertisements shown are generally keywords targeted i.e. compatible with the niche of the site. For example, if your site is related to real estate then the viewers can see the advertisements relevant to real estate. Contextual advertising is also called In-Context advertising. The advertisements shown on the site can be banners or pop ups. Advertisers pay the publisher when a user clicks on the advertisement. The most reliable and genuine contextual advertising program is Google AdSense. The CTR (Click Through Ratio) is very high when compared to other ad networks. The major search engines uses contextual advertising on their web pages. The advertisements are based on the keywords that users search in the search engines. Generally all contextual advertising programs allow publishers to filter the irrelevant ads. Basically the revenue model is CPC( Cost per click) or PPC( Pay per click ) . The other models are CPA( Cost per action), CPM(Cost per impression) and CPP(Cost per play). There are mainly 4 revenue models : 1. PPC(Pay per click) or CPC(Cost per click) - PPC or CPC is a revenue model where advertisers pay publishers when a user clicks the advertisements shown on the publisher site. CPCCost/Total Clicks 2. CPM (Cost per miles or impressions) - CPM is a revenue model where advertiser pays you on the 1000 impressions basis. When a user visits a page with a banner ad then it is counted as 1 impression. The formula to calculate the CPM is shown below. CPM is measured in Dollars. CPM(Cost/Total Impressions)x1000 3. CPA (Cost per action) - CPA is the revenue model where advertiser pays you when a visitor takes action like buying the product, signing up or filling form. 4. CPP (Cost per play) - CPP is the revenue model where you will be paid for running audio advertisements on your websites. In-Text contextual advertising programs : The other form of contextual advertising is In-Text advertising. When a user hovers over the double underlined keyword, In-text ad is displayed. You will be paid if any one clicks on the in-text ad. The market leaders in in-text advertising are Infolinks and Kontera. In-Image contextual advertising programs : In the recent years In-Image advertising has shown significant progress in the internet advertising market. The publishers embed the code provided by the ad networks to show the ads overlaid on images. When a user hover over the image ad is displayed. The advertisers pay you when user clicks on the ad. Gumgum, Luminate and Image Space Media are the market leaders in In-Image advertising. So, one can make good money with contextual advertising programs with the right strategies.