A keystroke I do frequently use with Firefox and similar browsers is [Ctrl][PgUp]/[Down] to get to the next/previous tab. Lately my X-Server got unusable because it did no more react on mouse clicks. It was still possible though to navigate with keystrokes. A special mouse pointer was shown and Xorg had stayed locked in this state all of what concerns the mouse. Independently from occurences like this one every good GUI program shall be navigable by keys only. You have standard keys like [Alt][Tab], [Alt][F3] and [Alt][F4] on your desktop and this is all what is needed to come for the rescue if your mouse should not be usable due to some reason. Besides this a mouse arm can be a health issue and using keys a speed/convenience issue.
A keystroke I do frequently use with Firefox and similar browsers is [Ctrl][PgUp]/[Down] to get to the next/previous tab. Lately my X-Server got unusable because it did no more react on mouse clicks. It was still possible though to navigate with keystrokes. A special mouse pointer was shown and Xorg had stayed locked in this state all of what concerns the mouse. Independently from occurences like this one every good GUI program shall be navigable by keys only. You have standard keys like [Alt][Tab], [Alt][F3] and [Alt][F4] on your desktop and this is all what is needed to come for the rescue if your mouse should not be usable due to some reason. Besides this a mouse arm can be a health issue and using keys a speed/convenience issue.