Google says some users of its free Gmail service and others may experience some problems as the company works to improve the system. "Users of all Web services may have periodic trouble with access, and as we make updates to improve and enhance Gmail, some users may see error messages and experience short periods of inaccessibility," a Google spokesman said in a statement Wednesday. "These errors are neither persistent nor pervasive, but we take all issues very seriously and resolve them as quickly as possible. We encourage these users to contact the Gmail Support team, who can investigate any problems. We're continually listening to feedback from our users and working to improve the product."