View selection source allows you to select a part of the content and then check the source. If you are looking for a CSS tag for instance, here is no way you will find it if you click on source only, like on a WordPress source code where here is so much javascript and all. You can just highlight one line and see the tags you are looking for in one second without scrolling. Only Firefox or alternative has it.
You can right click any part of the page and choose inspect this and the class for CSS will be listed right in the footer