Nothing can be more unsettling than an obvious problem with absolutely no error or diagnostic message, and that’s exactly what the infamous white screen of death is. Imagine that you were changing a setting on your blog, installing or upgrading a plugin, upgrading to the latest version of WordPress, or simply returning to your blog at the start of a new day, and you see nothing but white.
Unfortunately, the white screen of death became all too well-known in the WordPress community when a few incompatible plugins began to cause the issue after users upgraded to WordPress 3. Today, most white screens of death are either caused by plugins or themes (theme functions can sometimes interfere with core WordPress functions). If you want to immediately attempt to find the culprit, you can enable debug mode, but even that can produce nothing more than a blank screen, so why not attack the problem head on?
We’ll start with your plugins. If you have access to your admin panel, try deactivating all plugins. If you don’t have access to your admin panel, try manually resetting your plugins. If that resolves the issue, reactivate each one individually until you find the cause.
If your blog showed no signs of improvement after deactivating your plugins, then it’s time to move on to your currently active theme. If you have access to your admin panel, try switching to the Default theme (WordPress 1.5 – 2.9.2) or the Twenty Ten theme (WordPress 3.0 and higher). If you don’t have access to your admin panel, access your server via FTP or SFTP, navigate to /wp-content/themes/ and rename the directory of your currently active theme, which will force the Default theme (WordPress 1.5 – 2.9.2) or the Twenty Ten theme (WordPress 3.0 and higher) to activate. This will hopefully rule-out a theme-specific issue.
Though plugins and themes are the most common cause of the white screen of death, there are a few rare causes as well. If the above troubleshooting steps failed to resolve the issue, please contact the WordPress Support Forums.