When an Visitor initiates chat,If there is no one from Support Team member available to accept a chat, a message should be sent to the user letting them know that the next available technician will get back to them. After this message is sent, a case is auto-created and assigned.
Please suggest me how to achieve this.
See the document below,
Queuing options in Live Agent let you specify how incoming chat requests are handled when there are no agents available.
https://help.salesforce.com/HTViewHelpDoc?id=live_agent_queueing_overview.htm&language=en_US
Regards,
Ashish