* select type:
     1) horz+vert+9 squares
     2) horz+vert+9 squares+ 4 grey squares



samples:
===========
http://www.websudoku.com/?level=5&set_id=12199906296
5.. 8.. .6.
..7 ..3 5..
..1 .65 2..

..2 ... ...
18. ... .94
... ... 7..

..5 92. 6..
..8 3.. 1..
.7. ..1 ..8
===========
http://www.websudoku.com/?level=1&set_id=20025515738
7.9 ..5 3.4
.3. 24. .59
... ... 28.

..5 .7. .2.
... 538 ...
.1. .2. 5..

.43 ... ...
59. .87 .4.
2.6 4.. 8.1
===========
http://www.websudoku.com/?level=4&set_id=1016730526
..5 .79 4..
2.7 ... ..5
... ..5 ..6

.2. .6. 8..
... 5.1 ...
..6 .2. .4.

7.. 1.. ...
6.. ... 5.3
..3 98. 1..

===========
http://www.websudoku.com/?level=4&set_id=6622193123
.8. ... ...
91. ..4 ..6
5.. 9.3 .2.

.9. .71 ...
..2 ... 6..
... 63. .4.

.3. 1.5 ..7
4.. 7.. .18
... ... .5.
===========
http://www.websudoku.com/?level=3&set_id=6420954259
... ... 8.6
.1. 7.4 9..
4.. ..8 .2.

35. 2.. ...
.2. ... .7.
... ..5 .61

.3. 5.. ..8
..8 9.2 .3.
9.5 ... ...
===========
2011-03-05 ( nrc )
... 6.. ...
.6. 4.7 .3.
91. ... ...

.3. ... .8.
... ... .9.
... ... .1.

... ... 5.4
1.8 ... .7.
..2 ... ...

===========
2011-03-07 ( nrc ) --- level0 solver
... 6.. ..9
..8 ... ...
... ... 51.

4.. 5.6 3..
2.9 ... ...
.3. 4.. ..8

... 8.. 25.
.7. ..4 ..1
... ..2 ...

===========
2011-03-08 ( nrc ) --- level0 solver
... .25 ...
2.. ..1 ..3
.8. 3.. 92.

... ... ..4
7.2 ... ...
... .1. 3..

..9 ... 8..
... .94 26.
.6. ... ...

===========
2011-03-09 ( nrc ) --- level0 solver
... ..2 7..
5.. 9.3 ...
.7. .1. .9.

..1 645 ...
... ... 6..
..4 1.. 3.2

73. ... ...
... ... ...
1.. .2. ...

===========
2011-03-10 ( nrc ) --- level0 solver
.21 ... 3..
4.. ..8 .9.
..9 ... .68

... ..1 73.
2.. ... ...
... ..3 95.

.86 ... .47
.3. ... ...
... ... ...

===========
2011-03-11 ( nrc ) --- level0 solver
.9. ..5 ...
.31 .98 .2.
.6. .3. 9..

..7 ... ..2
... 34. .1.
6.. .1. ...

4.. ... ...
.2. ... .5.
... .6. ...

===========
2011-03-12 ( nrc ) --- level1 solver
.7. ... ...
.1. ... ...
... 3.. 4..

... ... 6..
... ... .4.
9.8 5.. 3..

..6 7.. 2..
..9 ... ..8
... 9.. ..1

===========
2011-03-14 ( nrc )
... ..1 2..
.5. 8.. ...
847 ... .35

.3. ... ...
... ... ...
..9 .8. 5..

9.. 7.. .61
7.. ... 48.
.1. ... ...