Column, Row Font Size

[Old Red One]

For some reason the column letters and the row numbers - at the very top and
far left on any worksheet - have become so small on a particular worksheet
as to be illegible. What have I done, and how do I undo it?

 

[Dave Peterson]

If it only happens on one worksheet, maybe you've set the zoom too small.

From the menu bar: View|Zoom... (and resize to look nice)

There's a Zoom icon on the Standard toolbar that you could use, too. (My icon
is at the far right of that toolbar.)