A white screen (the White Screen of Death) or HTTP ERROR 500 looks catastrophic and is usually a small thing. It typically happens right after an update or a new plugin. Go in order — do not skip.
1. First: what does the error actually say
The white screen hides the message. Turn on debugging: in wp-config.php (via cPanel → File Manager) find the WP_DEBUG line and set it to true, plus WP_DEBUG_LOG to true. Refresh — now you either see a message or wp-content/debug.log appears with the exact culprit (plugin name and line). That is 80% of the job.
2. If it is a plugin (most often)
Cannot get into admin? Via File Manager rename the folder wp-content/plugins to plugins_off — every plugin deactivates at once. If the site revives — a plugin is the culprit. Rename it back, then deactivate them one by one (renaming each) until you catch it.
3. If it is the theme
Rename the active theme folder inside wp-content/themes — WordPress falls back to the default theme automatically. If the site works, the theme is the culprit (usually after an update).
4. If it is memory
Seeing allowed memory size exhausted? In wp-config.php raise the memory limit to 256M. If it persists — your plan resources are tight for what the site demands.
5. If it is .htaccess
Rename .htaccess to .htaccess_old, then in admin: Settings → Permalinks → Save (a clean one is generated).
When to call us
If debug.log is empty, if the error returns after every fix, or if you simply have no nerves left — write to us. For maintenance clients we handle this — usually before you notice.