Sometimes, after installation of a new plugin your website can stop working – it crashes and all you can see is white screen with some enigmatic error code or other not less strange information. This view is called “WordPress white screen of death“. Fortunately WordPress is enough sophisticated to keep your website content safe in most situations. Plugins are designed in a way which prevents more serious scenarios. But, when something bad have already happen, the first step should be to go back to admin panel, to see if plugin’s deactivation is still possible. Deactivation of plugin can solve the problem. But, if you lost access to admin panel as well, try to get access to your web hosting account (for instance via FTP), where you can edit your website content and rename plugin’s folder. After this operation, plugin should be automatically deactivated by WordPress system. However, if it doesn’t help, try to remove plugin’s folder with all its content. After the described treatment all should come back to normal. If there are still some problems – let’s say you installed several plugins at one time and activated all of them at the same time – try to rename or remove all plugins’ folders one by one to find plugin which is responsible for website’s crash.
In case of more serious events – that is if in spite of the above described steps website is still in bad shape – the right treatment depends on functionality of installed plugin to get clue which essential WordPress files could be affected, to replace them, because replacement of some WordPress files can be sufficient.
Just in case, it is a good idea to make copy of WordPress database and all WordPress system files, before you install plugin or template.