Core Issue
When an attempt is made to use the WebDialer http call from the http: ///webdialer/Webdialer?cmd=doMakeCall&destination=xxxxxxxxxx# URL, Cisco CallManager does not accept the #, which results in delay in call connection as it waits for the interdigit timeout to expire.
Resolution
In order to resolve this issue, replace the # with %23, because this represents the # sign for the WebDialer application.
In that way, the correct URL is http: ///webdialer/Webdialer?cmd=doMakeCall&destination=xxxxxxxxxx%23, where xxxxxxxxxx represents the dialed digits.