When designing a page or a section for your website, you need to be careful about dimensions. Just like we use a ruler when we draw a physical blueprint, we need to use measures – and very precise ones – when we design our pages. In addition, when we look for inspiration on other websites, we may want to examine details like the height and width of various parts of the page. Measure-it is a super-useful ruler extension for Firefox that lets you easily take measures of anything you want on your screen. In addition to height and width, you can also examine the alignment of elements in pixels. It’s fast and extremely simple to use, and comes with the option of adding custom shortcuts to make it even more convenient.