HTML Tidy is able to correct many common errors in HTML files without any help from the user and display the tidied code in the Output window. However, some errors must be manually fixed before HTML Tidy can correct any remaining errors. If such an error is found, HTML Tidy will display a description of the error in the Messages Window.
If the Output window remains empty after running HTML Tidy:
Once any HTML errors are fixed, HTML Tidy should update the Output window.
If the Output window does not get updated even when there are no error messages in the Messages Window (after running Tidy on a new HTML file, for example), the system environment variable TEMP (or TMP) may not be present or may be pointing to a directory that's no longer present on the system. To verify if this is the case, open a Command Prompt window (or a DOS box), type SET, press Enter and look for the TEMP/TMP variable. Make sure that it is present and that it is pointing to a valid directory name that does not contain any special characters (such as C:\TEMP\).