Fixed! I wish I could report exactly what the problem was, but suspecting the HTML, and not knowing a whole heck of a lot (yet) about markup, include statements, you name it… I went ahead and tried a fix first.
In the editing window, there were blank lines I hadn’t noticed at the bottom of text I had copied and pasted in. Removed the blank lines and all was well.
Am determined to learn how everything works now; I hate trial and error.