When considering privacy and security of our data it is important to know what details grab by our browsers in day to day life and how they collect those data and how we can mitigate or prevent from being revealed ourselves.
To get know what details a website can grab through your browser visit following sites.
https://panopticlick.eff.org ; This site reveals your screen size and colour depth, browser plugins, time zone, keyboard language type, system fonts, platform and other things.
https://clickclickclick.click ; It is super for getting weird. This site shows your mouse location, whether it is moved or not. Time you spent in the site.
http://webkay.robinlinus.com/ ; This site shows your location, operating system, browser version, plugins, cpu cores, gpu details, battery percentage, local and public ip, isp location, social medias logged in, gyroscope if it is a phone or tablet without any button click. there are some other tests also. You can test your network by clicking on a button, demo of click jacking scenario and auto fill phishing demo. These tests indicates how any site can extract details from your browser and make those for malicious things. Important thing is using it's page source you can learn to write javascripts which can extract details (you can use its JS functions).
