Advice please

White to move c5

To my novice mind it advances the pawn with support from D4 and blocks off the dark coloured bishop from moving to B4 (maybe not a bad thing in itself). E3 could then follow shortly afterwards to make a diagonal bank of pawns. I have played it before but looking at the Game Explorer and the few times it has been used by good players, it is obvious that there is something very fundamently wrong with this move and my proposed line up of pawns..

Well I'm no expert myself, but i'll give this a shot.

the idea of playing c5 and then e3 to get a diagonal wall of pawns -- this could be countered by black simply playing b6, where you either have to break your wall or he will do it. 

Another reason, by playing e3 you'll be blocking in your own dark bishop in it's corner. 

You don't need to be worried about him taking your pawn on c4, because then you can play d4 and you have two pawns in the center of the board (which is good?  or so I've heard).

like I said, I'm no expert but I might play something like Bf4 or Bg5 here.  This will get your dark bishop active incase you do want to play e3 later... then your bishop won't be stuck in it's corner. 

Aye, the reason c5 isn't played there is because ....b6 and, if you play b4, ...a5 goes about destroying the pawn chain immediately.

The other difficulty with c5 is it releases the center tension too soon, thus relieving Black of a potential problem to deal with.  A threat is often more effective than the execution of a threat.  After c5, d5 is overprotected and his center and space equity are secure.  Also as stated, a pawn chain is only strong if it is secure.  c5 changes the target from Black and d5 to White and c5. 

OTOH, many club players will have a difficult time breaking the chain and mounting a proper counterattack in the center to foil your space advantage on the Q-side and pending attack there.  So while it may be good now as you progress to better opponents they will teach what is wrong with it.

It just wastes White's advantage.  It just leads to boring equality without putting much question to Black.

As a general rule of thumb you shouldnt release the tension in the center except to : 1 avoid disadvantage or 2 when it brings advantage to do so

and a " diagonal wall of pawns" is better known as a " pawn chain"