Whats an invalid session …?
A session is the period of time a user spends on a website or logged into an application on a website. A user session begins when the user accesses an application and ends when the user quits the application. If, for example, you are trying to register your details, get to the end of the process and receive an error message of Invalid Session, it will usually mean that there have been periods of inactivity during your registration and the website has decided to end your session. The session time for musicteach has been set to 20 minutes.