Screengrab is a add-on for Firefox that will help you to take the complete screen shots of a web-page very easily. All you have to do is to right click the web-page which you want to save and then hover your mouse pointer over Screengrab! > Save… > and than hit the Complete Page/Frame… After that, all that is left is to select the location in your PC where the screen shot of the web-page will be saved.
You can download Screengrab for Firefox from here.
