Agree with the above regarding Hillsborough.
However, i would argue that the laws implemented after the Hillsborough disaster, in terms of all-seater stadia, have somewhat improved the quality and standard of stadiums. Without them, we may have been stuck with old, crumbling grounds. (Although, BP may be argued to be just that.)
In my opinion, that 20 years has given a period of important change in football across England, in which behaviour at games and safety has largely improved. With this change, it is now apt that we can trial the re-introduction of a version of standing, most probably the rail seating system. Trialing this at various grounds across the country will provide an important step in the process, also having it in a big stadium (Such as Celtic Park, as they have already volunteered should the SFA let them) will be majorly important in Britain.
It works in Germany, so there's no reason it can't work for us!
100% supportive, love standing at grounds.