There are many types of events that a browser can throw. You can find a complete reference at https://developer.mozilla.org/en-US/docs/Web/Events.
As we know, each browser has its own set of instructions; therefore, we can classify events into the following groups:
Standard events: These events are defined in official Web specifications, and should be common across browsers.
Non-standard events: These events are defined for each browser engine specifically.
Mozilla-specific events: These events are used in add-ons development and include the following:
Add-on-specific events
XUL events