Getting error on Web.config's service part, when using a Web Chat AJAX code from MSDN

I took a web chat code from MSDN and while trying to implement it on my web form site, I get the following error

Warning	1	The 'contract' attribute is invalid - The value 'PlayZone.Services.SessionPool' is invalid according to its datatype 'serviceContractType' - The Enumeration constraint failed.	E:\Projects\PlayZoneJUNE04\PlayZone\Web.config	57	48	PlayZone

Warning	2	The 'name' attribute is invalid - The value 'PlayZone.Services.SessionPool' is invalid according to its datatype 'serviceNameType' - The Enumeration constraint failed.	E:\Projects\PlayZoneJUNE04\PlayZone\Web.config	55	22	PlayZone

which tells that there is some error on the SERVICES part of theWeb.config. Here is my Web.config's service part and let me know if there is any mistake in it

<services><service name="WebChat.Services.Transition"><endpoint address="" behaviorConfiguration="Sever.Services.TransitionAspNetAjaxBehavior"
            binding="webHttpBinding" contract="WebChat.Services.Transition" /></service><service name="WebChat.Services.SessionPool"><endpoint address="" behaviorConfiguration="Sever.Services.SessionPoolAspNetAjaxBehavior"
            binding="webHttpBinding" contract="WebChat.Services.SessionPool" /></service></services>

Thanks in advance and have a nice day ahead.