The reasons for this are simple.

• Even though the rubik's cube has so many uncountable squillions of positions that even an infinite number of monkeys with an infinite number of rubik's cubes busy turning and twisting for all their born days would still take longer than the age of the known universe to solve even one, believe it or not, there are even more ways than that of randomly arranging the pieces on the central frame.The proper 
• The upshot of this is that if you assemble the pieces at random, there's a 92 percent chance that even an expert cuber will not be able to solve it. Imagine the life of frustration and despair that would follow, as you then tried method after method to no avail, formula and algorithm failing time and time again, your rubik's cube's mottled faces forever mocking you...
• Anyway, now that I've said it, you have a perfect answer for the cynics who mocked you as you were dismantling it, and now say 'Aha! If you aren't cheating, why are you reassembling your cube in the solved position?' Tell them you have to, because I told you so. Show them the website, and say 'Satisfied? Cynic!'
• In case you are thinking, 'I'll play a trick on my expert cuber friend', trust me, it won't work. You are probably planning something like this
  • You will reassemble the cube randomly
  • You will pass it to an expert cuber to solve
  • You think you then have a 92% chance of watching smugly and giggling as your friend tries and tries to solve your impossible puzzle.
  What will actually happen is this :
  • You will reassemble the cube randomly
  • You will pass it to an expert cuber to solve
  • Two minutes later, the expert cuber will give it back and say 'It can't be done. You must have taken it apart, and put it back together randomly, either as a lame attempt at a practical joke, or because you didn't follow the instructions on The Rubik Zone'. 
  • This is no fun for you. You then have to take it apart again, and reassemble it in the solved position, just like I told you in the first place.

Anyway, on with the show.

Four edge pieces

The first four pieces are the hardest. There's so little for them to hold on to that they tend to fall out all by themselves. Collect four edge pieces that share a sticker colour (for example, I did white for this photo).

• With one hand, hold the pieces you've already done in place.
• With the other, slide in the other edge pieces one by one.
• You may need to slide them into a position off the face they belong to, and then twist them into place.
• When all four are in position, carefully place the cube on a surface, with these four edge pieces at the bottom.

Got that done? Was it very frustrating? Well, from now on, if you follow these instructions, there's not much chance that the half-assembled cube will begin to fall apart again. You should be able to make steady progress.

You are assembling the cube in the solved position, aren't you?

Four corner pieces

The four corner pieces on the bottom layer will just drop into place.

The Middle Layer

You should then replace three of the edge pieces in the middle layer.

• Yes, I said three, not four. You need the empty gap later.
• Slide the pieces down into their correct places

The top layer - first piece

It should be very easy to replace the first corner piece of the top layer.

The top layer - second piece

Using the gap in the middle layer, slide the correct edge piece next to the corner you've just done. You are probably wondering why I've got red pieces on the green face. Well, as long as the pieces in the top layer are all correctly positioned relative to each other, I can always give the cube a quick twist at the end to get it solved, right?

The top layer done - almost

Do the more top layer pieces like this - corner, edge, corner, edge, twisting the top layer each time so you can use the gap. Keep going until the top layer is all done, except for two corners and the edge between them.

Finishing the middle layer

It's time to slot in the last piece from the middle layer. Push it down, like you pushed down the other three.

Top layer - last corners

It's very easy to insert the last two corner pieces. Just rest them in their proper places.

The last piece

Finally, with the top layer twisted 45 degrees, you can put the final edge piece in place. Push it in, and you'll soon here a satisfying 'click' as it finds its proper home.

And that's how you reassemble a rubik's cube.

Err, you did reassemble it in the solved position, didn't you?

Anyway, here's a video version of the same instructions.