Problem inserting placeholder

[JFry]

On many occasions I have copied a link for a document or video saved in Google Drive and then right clicked on my web page and inserted a placeholder. It has always worked perfectly well. For some reason when I now try to paste a link the only option I am given is to paste replacing selection which doesn't work perfectly at all.

I have a main public site and a members' area which is in a sub folder. Looking at the design file, my pages in the members' area suddenly seem to have a dotted outline. If I drag the corner the page within the dotted outline becomes smaller, leaving behind the text.

I have obviously leant on my keyboard at some point and caused the problem. Could someone please advise me as to how I can sort it out?

Sorry, I should have said that similar pages where I have already inserted a placeholder are working okay still.