Most likely there is an error in your formula, so that it is
not doing what you expect it to do.

Try using the formula(s) on the spreadsheet itself in another
column to see if it generates True [number not zero] or
False [zero]. Conditional formatting only pays attention to
True and ignores any errors.

Conditional like normal cell formatting can be wiped out
or copied from another cell by pasting into a cell.

My page on Conditional Formatting is
http://www.mvps.org/dmcritchie/excel/condfmt.htm
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HTH,
David McRitchie, Microsoft MVP - Excel [site changed Nov. 2001]
My Excel Pages: http://www.mvps.org/dmcritchie/excel/excel.htm
Search Page: http://www.mvps.org/dmcritchie/excel/search.htm