What it does is, after downloading this extension a small icon will be displayed on status bar of browser. Once you click to on, and as we move the mouse over the page, corresponding color code (RGB) number is displayed in the status bar of the browser. Not only this, we can zoom the page that we are viewing and measure distances between any two points on the webpage. Know more about it from the home page.
On downloading this extension a MesureIt button will appear in the status bar or toolbar. Once you click to on, with the help of the mouse you choose any area, corner on the web page the dimensions of the selected portion will be displayed in terms of its width and height. To know more what MeasureIt is to offer, visit home page