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                  If you need to know which is the specific area your blog readers spend most of the time , then you need to add a heatmap script on your website . This heatmap is graph to tracking user behaviour on a site . Its not a common necessity every blog owner uses , but its for those who wantto study in depth iformation architecture and for optimization of link & advertisement placement.
I have tried to list all of the web conversion tools that are available out there - from free to paid versions , from open source to private companies .

1 Click Density 
Click Density is more and more of analytics and advanced tracking than a heatmap tool . As with other web analytics packages, you then paste this into the HTML for your website. You don't need any javascript or HTML knowledge, and full instructions are provided. When a visitor then accesses your website, a small additional javascript file is automatically downloaded from the clickdensity server - this usually only happens once for their entire visit, and has no effect on their browsing experience. Again you can choose to try free or purcgase full versions as well. Link .

2 Feng-Gui
Analyze Attention and Attraction in visuals. Check out how people see your website, creative media or photo and which areas of the image attract the viewer attention. Its not free but minimum price starts from 5$ .
A Pre-testing technology that predicts performance of an ad, before it airs, by analyzing levels of attention, brand effectiveness and placement, as well as breaking down the ad's Flow of Attention. Such Pre-testing can be used to identify weak spots within an ad and to improve performance, location of brand, to pull out the key moments for use in ad tracking, and to identify branding moments. Link .

3 UserFly
Provides instantaneous web user studies by recording user visits and letting you play them back to see every mouse movement, click, and form interaction. Conducting a user study doesn’t have to be expensive or a logistic nightmare. Now easily perform simple and cheap user testing with your real users. And it only takes one minute to set up! It come free of cost and rages to upto $200/month .I tried it and found it interesting  . Link

4 Codynamix
Cannoli is one of the open source heatmap tool written in Ruby on Rails. Codynamix is  based on Ruwa web analytics. It is free and to use it you need to request by mailing them site info and you may get an activation fast . I haven't tried it yet !
But If you are developer then you can get the latest code from github:

5 AttentionWizard
AttentionWizard too looks better choice and it uses advanced artificial intelligence algorithms to simulate human visual processing and attention. It creates an attention heatmap of your Web page instantly that predicts where someone would look during the first few seconds of their visit. This tool is more of a visual tracking tool than actual click tracking, so if you had a mock up design, just send it to this tool and it will predict you how a pair of human eyes will move along the design elements.
It also tenda to produce more focused hotspots because they are designed to simulate where the brain’s awareness is highest. By contrast, eye tracking and mouse tracking images tend to have more ghost-like halos that are simply the result of movements between the actual points of interest.
You can try free or even purchase plans . Check this link .

6 Click Heats
ClickHeat is too an open source project released under GPL licence, and free of chargeand is good heatmap tool showing clicks on a HTML page , hot and cold click zones.
Requires Javascript on the client to track clicks, PHP and GD on the server to log clicks and generate the heatmap. Go

7 Crazy Egg
One of the most famous and most used tool . It has more features like to check how much attention a specific website area gets from your visitors. Check content your visitors care about the most, what they read, and what they completely skip over. Its not available free but has comparatively lower prices . Link

8  Click Tale
Again well known tool  but not available free . Web marketers can now easily identify the boring areas in web-pages that most visitors skip. These areas increase visitor frustration and cause potential customers to abandon the site. Now problem areas can be identified, revised and monitored, significantly reducing abandonment rates. Very helpful to increase ad-based revenue by optimizing your advertising location and increase its impact. By analyzing where visitors’ focus their attention and changing ad placement accordingly, website owners can both maximize their revenues and design a clean webpage layout. Link 

Eight of em ! If you know any more , help us increase this list :)