In Classic ASP, handling errors properly helps you diagnose problems and provide friendly messages to users. ASP provides a simple way to trap runtime errors using On Error Resume Next and check the Err object.

Basic Error Handling in ASP

1. Using On Error Resume Next

This tells ASP to continue executing the script even if an error occurs (without stopping).

<%On Error Resume Next  ' Enable error handling' Example: Divide by zero causes errorDim x, y, zx = 10y = 0z = x / y  ' This causes division by zero errorIf Err.Number <> 0 Then    Response.Write "Error Number: " & Err.Number & "<br>"    Response.Write "Error Description: " & Err.Description & "<br>"    Err.Clear  ' Clear error after handlingElse    Response.Write "Result: " & zEnd IfOn Error GoTo 0  ' Disable error handling%>

2. Important Err Object Properties

3. Custom Error Handling Function Example

<%Sub HandleError()    If Err.Number <> 0 Then        Response.Write "<b>Error Number:</b> " & Err.Number & "<br>"        Response.Write "<b>Description:</b> " & Err.Description & "<br>"        ' You can also log errors to a file or database here        Err.Clear    End IfEnd SubOn Error Resume Next' Example code that may cause errorDim fso, fileSet fso = Server.CreateObject("Scripting.FileSystemObject")Set file = fso.OpenTextFile("C:\nonexistentfile.txt", 1)If Err.Number <> 0 Then    HandleError()End IfOn Error GoTo 0%>

4. ASP Built-in Error Object for Global Error Handling

You can create a global error handler in Global.asa file for your site with:

Sub Application_OnError    Dim errObj    Set errObj = Server.GetLastError()    ' Log or display error infoEnd Sub

5. Displaying Friendly Error Pages

• Configure IIS to show custom error pages instead of detailed ASP errors for security.

• Use <customErrors> in IIS or web.config (if using ASP.NET) or IIS error settings.

Summary

• Use On Error Resume Next to catch runtime errors without crashing.

• Check the Err object for error info.

• Use Err.Clear after handling an error.

• Consider logging errors for troubleshooting.

• Disable error handling with On Error GoTo 0 when done.

Want me to show you how to log errors to a text file or send error details via email?