website design - Back breaking sites

What's the reason that so many site these days "break" my back button experience?

Even stack does this: I read a question expand the comments, scroll to the first answer, follow a link, decide I'm not interested and press back.

At that moment, stack will have unexpanded the comments section and I will land on another place as where I left the site. This is very uneasy because now I have to search again where I had left the page.

There are a lot of other examples I could name, like slashdot.org where you can expand the comments, but when you follow a link and go back, comments become unexpanded and you lose track of where you where.

Also a lot of sites have "integrated forums" like disqus where leaving the site brings you back to the top of the comments if you press back.

What's the reason for these site to implement an imo very bad back-button experience?

Considering, back is the most used button on the browser.

Answer

There are three reasons for this behaviour:

1. 
   

   A lot of new web apps are utilising Javascript MVC frameworks and the concept of the single page app. In this context, in order tot make the sort of behaviour described work you need to use the history API. This is all very new technology and designers, developers and product managers are still getting to grips with it in many cases.

   
   


2. 
   

   It is technically difficult to do. You need to expend time to mimic behaviour that comes out of the box in a simpler, older implementation. The time and money for this might not be available.

   
   


3. 
   

   It is sometimes done for security reasons, for example, while following the steps to transfer money online where the service provider need to keep really tight control over the when and how the data is sent. Again, it is harder to get around security issues the back button might introduce than it is to just disable it

   
   
   

Having said all this, it does go against a pretty fundamental usability guideline, that one shouldn't hijack the back button. A website that really wants a strong user experience and doesn't have any security concerns (read that as all but one in a million) should make the back button work as expected as most users expect this to work.