Readers who've heard of the argument for an intelligent designer based on the fine-tuning of the universe, but aren't sure what, exactly, the argument is can find an excellent summary in this excerpt from the film Privileged Planet:
Dozens of these parameters and constants are set to unimaginably precise values. In some cases the tolerance for error is as little as one part in 10^100. Deviation of just that much from the actual value would result in either no universe at all or a universe unfit for life.
When one considers that there are only 10^80 atoms in the entire universe the unimaginable exactitude with which it is put together is breathtaking.