How to create a custom error page in Joomla
Making a custom error page for a Joomla website can add an extra touch for your website. Besides, it’s way more helpful to your users. If a user ends up on a default error page, chances are that he will exit your website. But if you have customized your error pages which explain why there was an error, there are more chances that the user will continue. Therefore, let’s create a custom error page.
The error page in Joomla is in /templates/system/error.php. Copy the file to the root directory of your pattern. Now you can modify this folder, thus in case you recognize PHP you may create altering it. The difficulty is that it will not be very simple to comprise modules such as your menu, your module or additional modules.
Create a new article for the error page. Creating the error page can be as simple as copying the default error page script, copying it and making slight alterations.
In the Article Manager, find your latest article in the register. In the column, you will find the ID of your article. You need this to connect it your article.
Now you must connect the article to the error page that you have created. After that, you will have your custom error page created.