Is it considered cheating to consult books while playing online chess? For example if one is weak on openings can one consult with MCO while playing?

No it's not cheating. Any 'static' resources like books, videos, databases etc are allowed in Online Chess. No outside assistance is allowed in Live Chess though.

Thank you little one. If no one has a contrary opinion on this subject I will be checking my books and notes whilst playing online chess.  

Good luck to your games frank :) 

See this help entry  http://support.chess.com/Knowledgebase/Article/View/13/3/what-are-the-rules-for-playing

"Openings books and game databases may be consulted for Online (correspondence-style) Chess only"

ok ty

Hi Frank. . .

I take Online games under a different philosophy. Online games can be used, not only as serious chess games, but also, and most important, as a studying medium. . .so. . . what is wrong with consulting books?

Note.

In Tournament games I think it sould be cheating. . . but if you are allowed a couple of days to move. . . who assures that your opponents are no mean while "consulting" ?

"To be or not to be" said a great "somebody".