Changing the default file association in Gnome 3

For some strange reason on my machine Signal had taken over as the default program for HTML files. Or, in other words, if I clicked on an HTML file such as index.html then Signal would automatically open instead of the file being opened in Firefox or Gedit or something reasonable. How I managed to get a messaging program to do this is a mystery to me, fixing it is quite easy though.

1. Go to the file you want to open in Nautilus (The Gnome file manager) and find the file that is giving you problems.
2. Right click on the file and choose Properties.
3. Open the third tab of properties called Open With.
4. Find the program you want to open the file with an select it.
5. Click Set As Default on the bottom right to set that program as default.