1. Checkdigit shows whether Air waybill contains a mistype.

2. Instead, the sender probably mistyped or forgot the correct address.

3. In the code 404, the first digit indicates a client error, such as a mistyped Uniform Resource Locator (URL).

4. Another common cause of "File Not Found" errors is accidental mistyping of URLs, either directly in the browser, or in HTML links.

5. You can use this feature to keep Copy from treating a mistyped destination directory name as a file name and attempting to append all your source files to a single destination file, when you really meant to copy them individually to a destination directory