Is there a way to identify custom tag files? I mean may be the site I have contain custom tag files and I don't know about it? In this case I will just set its path in ColdFusion administrator and it will work!
Do these files have a certain extension? Or a certain naming convention for .e.g since this custom tag is "selectdate" so its file must be by this name?
How do I identify a custom tag file?
As Dan says, they're just CFM files. Usually one can identify them as follows:
* they're in the same directory as a file calling <cf_somefilename[...]>, wherein there is a somefilename.cfm is the name of the file
* they're in one of the directories set as custom tag directories (in CFAdmin, or Application.cfc)
* they have references to "thistag" or the attributes scope in them (although the latter can produce false positives on Fusebox sites)
By the sounds of it, your issue is - like I said before - you haven't got your custom tag dirs set up in CFAdmin (or in Application.cfc, which I didn't mention before). Investigate that.