OS X Mail Mavericks 10.9 Gmail accounts NOT in sync In OS X Mavericks 10.9.2 after doing all the updates my Gmail accounts still show messages that are in the inbox but when I login to gmail on the browser, they aren't there.

Is there a way to fix this? I don't remember this happening before. I am using IMAP.

I use IMAP on OS X and use the exchange setup on my phone/iPad. All my accounts are gmail.
Try "Get Account Info" by right-clicking on the mailbox, which will force Mail to search through the IMAP account for messages and seems to rebuild all mailboxes in the account.

See this answer for further suggestions if that fails.