How to get missing grid lines back?

[Larry Alkoff <labradley mindspring com>]

I have a spreadsheet started by a clever fellow that likes to "pretty 
print" who has left the company.

There are large sections of the spreadsheet with no grid lines.
The cells exist because I can click on where a box should be and it is 
outlined.

Sometimes the vertical lines are missing, sometimes the horizontal 
lines, sometimes both.  It's very disconcerting.

Another thing is some of the grid lines that exist are bold, some are 
not.  How did he do that?

How can I get grid lines back?

Larry