Read the FAQ in the 1st post.

FAILOVER

Use "epools.txt" and "dpools.txt" files to specify additional pools. These files have text format, one pool per line. Every pool has 3 connection attempts.
If the first character of a line is ";" or "#", this line will be ignored.
Pool specified in command line is "main" pool, miner will try to return to it every 30 minutes if it has to use some different pool from the list.