Don't break my Back button

And by "back button" I mean mouse gesture, two-finger trackpad swipe, keyboard shortcut and dedicated physical back button as well as the traditional back button in a browser. Whatever the means of execution, I want it to work reliably and predictably, every time I hit it, regardless of my current location, unless I have explicitly instructed the browser to break the convention, for example by opening a link in a new tab.

The issue is simple and is highlighted by the way the two-finger swipe works in Mac OS X Lion. If you swipe two fingers from left to right on the trackpad it triggers the back operation and returns you to the previous screen (with visual feedback via an elegant animation - it's as if you were brushing the current page out of the way to expose the page underneath). It's neat, easy and surprisingly noticeable once it doesn't work, which happens for a number of reasons:

• Websites that open pages in new tabs when it isn't logical to expect them to do so. Ok, fine, if it's a link to a totally separate site from a catalogue page, then maybe a new tab is appropriate. In all other situations, reuse the existing tab so that you Don't Break My Back Button. Opening a completely new browser window is also out - it's so 2006. 
• Strange website behaviour and redirections. If I follow a link from the search results on your website I want to be able to return to the search results when I've finished looking at the page you've offered me. I don't want to have to start from scratch and re-enter my search criteria just because you've got some funky feature that breaks my back button and prevents me going back to my results. 
• Applications with “back” functions that insist on using buttons. Unfortunately Apple are one of the main culprits of this particular problem. iTunes and the Mac App Store both have forward and back functions that don’t respond to the two-finger slide; it’s surprising how quickly the absence of the two-finger slide becomes extremely annoying. 
• Any site that “returns” you to your current page, for reasons unknown, is either poorly designed or deliberately broken (or both). Blogger, I’m looking at you (try looking at a post in edit view, then swiping back to the list of posts). 

One of the things that makes the web easy to use is the fact that there are conventions about how things are done - search boxes top right, home button top left, navigation at the top etc. - mess with these conventions and you make your website more difficult to use. Difficult websites discourage visitors by obscuring the information you want them to have. Broken or novel navigation features also trip users on their way to your content. The simple rule is to deploy new conventions only if you are absolutely certain that they will make life easier for your users. In all other cases, don’t.