CSS HTML Validator features two update checking mechanisms.
You can perform a standard update check by choosing Help->Check for Updates. CSS HTML Validator will contact the server and display a dialog that will let you know whether you're using the latest version.
Periodically, you may also be asked (reminded) to check for a new version at startup. You can disable this question in the Startup Page of the Editor Options.
The "quick update check" method automatically displays a short message in the status bar at program startup, every x number of days, with the default being every 7 days. In addition, for more important update messages, the message may appear in a dialog box and the computer may beep.
To change how often the quick update check is done, change the registry entry "QuickUpdateCheckDays" in "HKEY_CURRENT_USER\Software\AI Internet Solutions\CSE HTML Validator v4\Editor\Interface". Set the value to the minimum number of days between checks.
To disable quick update checking altogether, make sure that the bit representing 0x80000 (or 524288 in base 10) is not set in the registry entry "Flags4" in "HKEY_CURRENT_USER\Software\AI Internet Solutions\CSE HTML Validator v4\Editor\Interface".