I know ClientID is used for javascript and UniqueId for server side and that ClientID uses an underscore (_) and UniqueId uses a dollar sign ($) in asp.net 2.0. But what I d
this.UniqueID is the control's name appended with all naming containers, think of it as the fully qualified control name. this.ClientID is the value that will appear in the id attribute of the control, it is a translation of the uniqueid to be a (well almost) html compliant id tag (leading underscores are not really html compliant).