One of the most irritating things a web site can do is to break the expected behavior of the Back button in my browser. So by using inappropriate caching settings, a site can make it so that the Back button refetches content, which makes it slower and introduces the possibility that the fetch could fail. Even worse is sites that do little redirect tricks so that using Back doesn’t work at all and you just get redirected right back. You can of course defeat this by going back 2 instead of one, but every time that I have to do this I grit my teeth. Some sites have their own Back navigation links – something which I don’t really understand or use. The Back button is a standard part of the browser – why not use that? The user always knows where the Back button is and it doesn’t take away page real estate from your content.
These are both part of #1 of Jakob Nielsen’s top ten new mistakes of web design