I'll guess your number!

This one always works. But it's not magic. (Unlike many, it's not math, either.) First, check it out. Can you guess?

It's pretty simple. On the first page, when you pick your number, the choices are in a scrambled grid (I've changed their colors to ones that work on my background, but the distribution is the same as theirs) :

9	21	4	22	7
13	18	11	23	15
8	1	26	5	16
14	24	17	3	2
20	10	12	19	6

You can, of course, ignore all the counting, repeating out loud, and so on. Just pick a number. Then you click on the color of your number. This takes you to the next step. Here you click on a color. This step is completely meaningless. You can click on your number's color, or not. It doesn't matter. It's a distraction, meant to get you thinking about colors. The click takes you to the next page, where the real trick takes place.

Here you're asked to choose the house that has your number in it. Here's the kicker:

House A: 4, 12, 1, 30, 11, 13

House B: 10, 26, 24, 9, 21, 2

House C: 17, 25, 14, 20, 8, 28

House D: 3, 23, 22, 27, 19, 5

House E: 18, 16, 6, 15, 7, 29

See the trick? No? Compare those sets of numbers with the grid.

Each house has one number from each color, plus a number that wasn't even on the grid to start with.

So you see, if you tell the program the color (say, white) and the house (say, C) your number must be 23. It's the only white number in House C.

The "pick a door" step is more razzle-dazzle. The computer (unlike a magician) can put any number it wants wherever you click.

Flashy, but just a trick.

You can look here for more such internet magic tricks explained.