GitHub is awful for this. If you're not signed in, the whole page is taken up with a giant signup UI, then in the top right there is another signup button. Ne

GitHub is awful for this. If you're not signed in, the whole page is taken up with a giant signup UI, then in the top right there is another signup button. Next to the signup button, there is a sign-in button, but it has no border and is so deemphasized that if you don't know it's there it blends into the other useless links in the top bar.