Computer challenge

I'm sure everyone has tried to practice against Fritz or Chessmaster set to a weakened playing level. Then they realize that, instead of playing like a 1200-strength human being, the computer makes GM-level moves then every so often "deliberately" drops a piece.

Below is a list of online computers that behave more consistently and realistically. They are listed in increasing playing strength. Test yourself against them and see where you stand. Post your best games if you want (ESPECIALLY if you manage to beat the 5th computer -- online Shredder on "Hard" -- without clicking the "Undo" button!)

1) www.postcardchess.com/computerchess.html (very weak, 1100-1200 strength)

2) pine.cs.yale.edu/java/chess.html (1300-1400)

3) http://www.chess.com/play/computer.html set to "Hard" (1600-1700)

4) www.ludochess.com/jester_eng/jester_eng.html set to level 10 (1900-2000)

5) www.shredderchess.com/play-chess-online.html set to "Hard" (2200+ master strength???)

*PS: these links are not meant to advertise. These websites present absolutely no competition to chess.com, so please don't delete this!

thanks for the links of the Computer challenge