I really like the opening trainer over at lichess.org.
A website to practice openings?

Thanks, I'll look into all the suggestions - was thinking of getting premium. @brettjames11 a good way to get comfortable with a certain opening is to play it many times against a computer as sometimes you can't always expect your opponent to go into a variation you want to look into.

Select an opening that you want to study, and go to chessgames.com and do a search on that opening. Find the "best players" for that opening and spend time going thru about 10-15 moves of a bunch of their games.
Then you practice by going to a random place (moves 5 to 10) in a particular game opening and guess the correct move.
Then go to chess-db.com and play Magnus or other GM' on the chess engine for the first 15 moves and see how you do in a "real" game.
Hi,
Sorry if this has been asked before but I was wondering if there is a site where one can set up the board so it is 6/7 moves into a certain opening and then play against a computer from that position. (Or is this possible to do on chess.com?)
Thanks in advance!