Report website compatibility issues at webcompat.com
The webcompat.com reporter extension adds a button which allows users to report issues with any site on the web. A screenshot will be added to the bug report, but you have the option to remove it before submitting a bug.
Sometimes, sites have bugs or policies that prevent them from working well in every browser. The community at webcompat.com works to help web developers and site owners identify and fix such issues.
If something appears broken, but works in another browser, or if a site or app insists you install another browser this is likely a web compatibility issue that you can report with this add-on.