I think a good idea in live chess for long games 15 or more would be to have the ability to move the piece with your mouse to the spot you want it in & then have to click ok. The reason being is that a few times I actually had a good game going, but lost it because the mouse slipped on one move,ended in the wrong square,  and totally turned around the game with a move that comes out as a blunder. I know Iv'e played other too who at some point made a slip with their mouse & lost their games to me because of it. There is plenty of time in the long games to have this feature without taking away a lot of time from your moves.

yeah I've slipped on that a few times, but I'm learning to stop because it is kind of like playing over the board which makes sense.  don't touch it if you're not going to move it and then once you let go ... done deal

yeah i've had mouse slips as well. that is, i'm moving the piece i want to move to the square i want it to go to, but i accidentally let go of the mouse button and drop the piece a square or two short from it's target square. sucks, but not much you can do i guess.

If you are concerned about mouse drag errors the best work around is to click once on the piece you want to move then release (it will highlight in blue), then click on the destination square.  

This makes the move and you don't have to worry about about a slippery finger while scrolling.

This is frustrating when it happens. I quit playing at one site because it seem to occur too often. Apparently their internet would drop out for short periods and it would not register your full move on long piece moves.

OTB, the rule rule is, you touch it, you move it. On the internet, this should be enforced but I have not seen it done: there may be sites where it is. But there is nothing a site can do that I know of where a player inadvertantly lets go of the mouse button too early if the mouse button is the signal that the move is over. A possible way around this is to have a system where you point the piece to move and then the final location but this seems a bit tedious. An alternative might be to allow algebraic notation for input which would be good when mouse batteries die as mine do every so often.

no no .. i agree with trigs, i've done that a few times also .. dropped the piece before it reached the intended square ....  but at first i would forget that it wasn't like the "turn-based chess" where you can move to piece and then click to confirm the move. 

the best way to solve that is do what Fookatook said with highlighting the square blue .. when you are sure of the move.

i've suggested this before to chess.com. eric seemed to think it was a good idea, but i'm assuming it's way down on the list of updates.

not only is it good for this issue, but it also is very helpful just for beginners to learn the notation.