By the way here's Phil's tips for a great mig weld.
1. Clean up area to be welded COMPLETELY.
2. Use a shade dark enough for protection but NOT SO DARK YOU CAN'T SEE. A #8 works for me.
3. Weld hot and slow. Use a steady hand. Don't jerk around.
4. Try to get your elbow braced against something. If you can't, consider using your off hand to support your torch hand.
5. Buy a nice angle grinder. Even the crappiest looking weld doesn't look half bad once you've ground it mostly flat, painted it, and brushed seam sealer over the top of it.