I've updated a typo3 website from 4.5 to 6.2.9. Now the issues with old extensions are fixed. But now I'm facing an issue with real url extension [ver.1.12.8]. If it's disabled the front end is rendered with no issues. When the extension is enabled it shows this error
#1294587214: Configuration Error: 404 page "D:/Xampp/htdocs/project125/404-melding.html" could not be found.
Best How To :
It appears, that you have the following value in your LocalConfiguration.php
[FE][pageNotFound_handling] = READFILE:D:/Xampp/htdocs/project125/404-melding.html
With this configuration, TYPO3 handles a pageNotFound event by displaying the content of the file configured (in your case
D:/Xampp/htdocs/project125/404-melding.html). When the file can not be found, TYPO3 throws an exception with the code
Try to check, if the configured 404 HTML page exists in your filesystem and if not, create it. For further debugging purposes you could also set pageNotFound_handling to "true" or "1" to show an error message instead of an individual 404-page.
Also make sure you clear all caches and also the RealURL encode/decode cache.