We have been doing at work with our web product for quite long time and it works well. Instead of simply showing a 500 page when an error happens and logging it

We have been doing at work with our web product for quite long time and it works well. Instead of simply showing a 500 page when an error happens and logging it, we also provide a link to let the user add information and comments about what he was actually trying to do. This helps us a lot to figure out how to reproduce the problem (it can sometimes be hard to do if it's a problem that only 1 user on over 100000 is having).