It depends on the browser and changes Google has made to the interface. In Firefox, a configuration change may allow copy, cut and paste to work, unless a document is locked, of course.
- In the URL bar, enter
about:config.
- If this is the first time you've done this, click to acknowledge that this might, "void your warranty".
- In the search bar, type
clipboardev.
- If
dom.event.clipboardevents.enabled is set to false, double-click it to set it to true.
Caveat: On some web sites, the converse happens, where copy, cut and paste are blocked when dom.event.clipboardevents.enabled is set true (e.g. for password entry), so make a note to yourself to set this back for those sites. sigh