Symptom

If you can't view the content of the file CHM file, all topics appears in blank or the message "Navigation to the webpage was canceled" appears. Usually this happens from Window Vista and recent versions.

Solution

Follow this steps:

• Before open it make a right click
• Select "Properties"
• In the tab "General" on the bottom select the option "Unblock"
• Now open the file and you will be able to view the content