Jianjun’s Blog

I stayed up late last night and was up early this morning. But it didn’t help with my WordPress blog’s ‘404 Not Found’ problem.

Actually it happened yesterday afternoon when I installed a plug-in that tampered with my .htaccess file. The install document was so badly written in some sort of English that in the end I was driven nuts and uninstalled it. I manually removed the part that it inserted into my .htaccess, but didn’t realize I probably mistakingly deleted/altered some of the old codes along the way.

The home page looked fine but all permalinks returned a ‘404 Not Found’ error - and I didn’t find that until this morning when I checked visitor statistics! If you experience a similar problem, i.e. you can visit the home page of your database driven site (not necessarily WordPress) but each individual page returns a ‘404 Not Found’ error, check your .htaccess file. It’s not your database problem.

After upgrading from an earlier version of WordPress to its most recent release 2.5, some people got this error message when adding a picture:

- Fatal error: Call to undefined function wp_constrain_dimensions.

This problem is caused by a corrupted upgrading process. To solve the problem, you must overwrite the old files (It is recommended to delete the old files first, then upload new ones) under the wp-admin and wp-includes folders. For root folder (where your wp-configure.php file resides), leave wp-configure.php intact but overwrite all other files.

For more detailed upgrade instructions, read WP’s Three Step Upgrade.