Can you counter a Land in Magic the Gathering?
Nope; it's a land (which is a special kind of not-a-spell card), not a spell.  In particular, a land never goes on the stack (where all the spells go); it goes directly from your hand into the battlefield as a permanent.

(If you could, it would completely not be a waste to counterspell a land.  Magic works on a steady acceleration of bigger and better spells as more land comes out.  Anything that puts your opponent a turn behind on that curve is useful.  Destroying/countering a land is about equivalent to delaying everything your opponent does for the rest of the game by one turn.)