Error in my ASP.Net application

Try this:

Create a simple test.asp file in the virtual directory you just converted to Application in step 3 above, with just <%Response.Write(“test”)%> in it. See if it runs okay. It should. If it doesn’t, and it’s giving you error that complains about parent path, double click on the virtual directory you just converted to application in step 3 above, and double click on the ASP icon in features view. Set the enable parent path to true. While you are at it, under the debugging properties, set send error to browsers to TRUE, so you don’t have to hang yourself later trying to figure out what’s wrong with this world(or IIS). If you are using IE as your browser, make sure to turn off “Show friendly HTTP error messages” so that you can see the actual error(Internet Options, Advanced).
At this point your ASP page should work fine. If not, make sure you do all the above steps right. If you are still getting an asp error, make sure you comment out “on error resume next” statement in your code.

My asp.net application works fine
It is located in inetpub sub folder

I don't know why anyone /anything would be trying to access a file test.asp
Test.asp doesn't exist
So how could this error occur ?

1.

Are you finding this error on your Windows Event Log?

2.

Try to find the IP Address Location that is making the request using an IP Location Service

3.

Is it normal to get visits from that location?
Someone (or a bot) could be trying to find a vulnerability in your system

How often do you get the error? Is the application live or on development server? LAN or WAN?

1. No from .net exception
2. I know IP from user logged in at time
3. New user

live server , happened once

If anything is pointing to that address within your application, so this is a "user error", someone misstype the address or is trying to find "something".    If your server is updated and well configured, I wouldn't worry about that.