A custom control that was placed in the title bar (in a master page) has since been removed, but some users still see it, even after clearing their browser history and doing a Control-F5 refresh. The people who so see it are using IE 11, although others also using IE 11 no longer see the control. I would appreciate any ideas to help all the users properly see the site as it has bee

Is this a publishing site? If yes, has the master page been checked in and published?

Thanks, the page was not checked in, and that solved the problem.

Through some mechanism I do not understand, the updated master displayed on my workstation (in three different browsers) where I had modified the page in SharePoint Designer even though it was not checked in, which I guess is how I managed to overlook checking it back in. I don't understand that, but there it is.

If anyone can shed light on that, I hope they will chi

If an item is checked out then the only person that will see the changes is the person that checked it out (which in this instance was you hence why you could see the changes regardless of which browser you use).

If an item is checked in (but not published - if you have draft versions enabled) then the changes will be visible to either users with edit access, or users with read access - depending on how you have set this up in the Versioning Settings of the List/Library. This comes under Draft Item Security where you can choose who can see draft items - "Any user who can read items", or "Only users who can edit items".

If an item is published then everyone with access will see the changes.