How do I avoid the "#DIV/0!" error in Google docs spreadsheet?

I have a column with average(K23:M23) that starts out with #DIV/0! when the K23 through M23 cells are empty. Preferably I'd like to only do the average of cells that contain non-zero, non-blank values. I think it's possible using the query command:

https://docs.google.com/support/bin/answer.py?hl=en&answer=159999

But their example doesn't help me.

How do I avoid people in my class?

To ignore someone, avoid making eye contact with them and pretend that you're busy with something. For example, you could pretend to be reading something or talking on the phone. Also, try taking different routes to school or work and avoiding their favorite hangout spots so you're less likely to run into them.

Wrap your formula with IFERROR.