Hover over the "green corner" or click on that cell and you should get
a little message or drop down menu explaining what it is. Usually,
it's a number or formula that is unprotected or inconsistent with the
others around it.
And if you don't like them (like me) you can turn them off under
tools>options>error checking
--
Regards,
Peo Sjoblom
Excel 95 - Excel 2007
Northwest Excel Solutions www.nwexcelsolutions.com
"It is a good thing to follow the first law of holes;
if you are in one stop digging." Lord Healey