If you ever need to take a screenshot of a website, Awesome Screenshot could make your life easier. Once you've installed the extension, you just click the camera icon, and Awesome Screenshot takes a snap of the whole page, even the parts that you can't currently see. You can then annotate the picture with lines, text, and more, and even blur out sensitive information before saving or uploading the image.
Note: This link takes you to the add-on's page at Mozilla.org, where you can automatically install the file into your Firefox browser. This program is donationware. It is free to use, but the author accepts and encourages donations towards further development.