How to add a report an error button in a Drupal 7 website and collect user's browser details? We just did a website upgrade. On some sites I have seen a 'Report an error' icon (in the right hind corner). After clicking on it, a user can report an error which will send along other information about their system like OS, the user's browser and what link they were on when the error occurred.

Question: Any suggestions on which module to use for it and/or how to add such 'Report an error' to the website?

Update: I am looking for something like whatismybrowser.com, which can be added like a button or tool.
You could check out the Feedback module to see if it meets your needs - it's pretty simple and lightweight. If you don't want to use a contrib module, you could do something similar to the Feedback module - create a block (either using existing blocks in your theme or create a new block region programmatically), position it absolutely, and then link the 'Report an Error' block text to some kind of web form where you can collect the desired information. You could also use the Webform module to help you quickly create a form.