Thanks Sheeloo and T. Valko but I still have questions about this issue. I'm
just copying my new questions on this new post to make it easier or you may
refer to my first post where I wrote them originally.

The original issue is after these questions.

I use Excel 2000 so I don´t have the FilePage SetupSheet tab
Under Print...Cell errors asselect blank OK option available.

The =SUMIF(A1:A10,"<1E100") formula helped me but would like to know what
does "<1E100" means.

About the AVERAGE formula =AVERAGE(IF(ISNUMBER(A1:A10),A1:A10))
I would like to know why should I use an array formula (in fact it worked
but just to know why)

And about the =IF(ISNA(your_formula),"",your_formula) formula, maybe I get a
blank cell to SUM or to AVERAGE but I get a mark on my chart just on that
month I'm using it and if I substitute the "" for NA() I get the #N/A mark on
my printed files.

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I'm using a formula to bring results from another worksheet but in some cases
I get the #N/A result as I don´t have data on the original worksheet. To get
the graphics on the final worksheet I use the formula with NA() not to give
me 0 values on the chart and I also use the conditional formula to get the
#N/A results just like the cells were empty (the same color I use for that
cell) but when I print my page, I get the #N/A in black (so I can see them)
and additional I'm not able to get a SUM or AVERAGE on each column as I get
the #N/A for those cells with that mark.

Two examples of the formula I'm using a

=IF(SUMPRODUCT(--('2009'!$B$8:$B$256=$O14),--('2009'!$B$8:$B$256<$O15))=0,NA(),SUMPRODUCT(--('2009'!$B$8:$B$256=$O14),--('2009'!$B$8:$B$256<$O15),('2009'!E$8:E$256))/SUMPRODUCT(--('2009'!$B$8:$B$256=$O14),--('2009'!$B$8:$B$256<$O15)))

=IF(L9/L8-1=0,NA(),L9/L8-1)

How may I get the SUM or the AVERAGE for that column and how may I print my
file without seeing the #N/A's in black?