Catch division errors with IFERROR
Dividing by an empty cell or a zero gives #DIV/0!, and one of those in a column is enough to break every total built on top of it. IFERROR takes a formula and a fallback: if the formula errors, show the fallback instead.
It is worth being slightly suspicious of IFERROR. It hides every error, not just the one you were expecting, so a genuine mistake elsewhere in the formula disappears behind the same tidy zero. Use it where you know exactly which error you are catching and why. Here, a campaign that has not run yet legitimately has no click rate.
In D2, work out the click rate as clicks divided by impressions, showing 0 when there are no impressions. Then fill D2 down to D6.
The grid for this exercise is part of the paid half.
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