Last updated at 11:23 a.m. PT.
Yahoo said it's working to correct an issue with its Yahoo Mail service that has left some users without service or with very glitchy service, according to the company. The problem also may affect other Yahoo sites.
"Yahoo Mail, Messenger and other areas of Yahoo may currently be inaccessible or slow to respond to some users in certain locations," a spokeswoman said in a statement e-mailed to CNET. "We are working to correct the issue and restore all functionality immediately. We know that this may have caused some inconvenience and we apologize to our users who might be affected."
The Yahoo spokeswoman did not say when the service would be fully functioning again or what is causing the issue.
As users logged in today, they were greeted with a window asking them to accept a terms-of-service agreement before entering the site. Even when users agreed to the terms, they couldn't access the service, many users complained via Twitter.
The terms of service are not new, the spokeswoman said.
Update, 5:28 p.m. PT:Though the service seems to have been back up all afternoon, Yahoo sent out the official all-clear this evening: "Yahoo Mail and other services are restored. We know that this may have caused some inconvenience and we apologize to our users who were affected." Still no response on what caused the problem.