In v7.7.x+ we begun using HTML5 "requires" coding, which will highlight fields which are required to be filled out in each HTML form which are empty or contain an invalid value.
If you're trying to update "General Settings" and something will not process, go through each "tab" and find anything with a red box around the input box (the "tabs" for the general display settings are "general", "date & time", and "HTML Includes"); be sure to check any regions that will need to be expanded (with a + sign).
For further information, please see
This Post for more information.