There can be many reasons for getting blank white pages or 404 error pages with a Joomla 3 installation. In this article, we will cover some of the more common reasons for these errors. If your pages are not coming up correctly, it is best to go through the checklist to rule out any of these easy to fix problems.

Backup, backup, backup

We can not stress strongly enough that you should ALWAYS do frequent backups of your Joomla files and associated database. On top of these regular backups, it is good to do a backup of everything right before installing a new extension. If you site goes down, you can restore it to its previous state relatively quickly. Do not rely on your hosting company for providing a backup. You may not notice a problem for a day or two and then it may be too late. If your hosting environment does not provide an easy way to backup both your files and your database, and be able to download these files to your local computer, then we suggest that you find a new hosting company.

Test major changes and upgrades on a development site

It is also suggested that you install a copy of the working site and copy of the database to a local computer or a subdirectory in your files on the hosting server. Link the copied site to the copy of the database so that the two sites are linking to separate databases.

Run the upgrade, test the new extension, or enable the plugin on the cloned site. Get the bugs worked out and be sure the site is running smoothly. Restore this new site and the new database to the main Joomla folder on the hosting company server. You still will need to make some changes to the configuration.php file when you move the site back and forth as the file paths will be different.

Problems right after running an upgrade

Often, when you run a Joomla upgrade you will overwrite changes that you or someone else has made to the core files or to template files. There may be changes that were made to the PHP that breaks your site when the settings are put back to the standard core files.

The problems that you are having can be that you upgraded the core Joomla files, but you have not upgraded the 3rd party extensions installed on your site. 

You may also need to upgrade your template when you upgrade Joomla. If edits were made to the templates style sheet files, you may need to put the old style sheets back into the template. The best policy is to create your own unique style sheets that load after the templates style sheets. These custom style sheets will not be overwritten when you upgrade.

Before running the upgrade, turn on Error Reporting in Global Configuration under the Server tab. This way, the errors for the site can show if the blank white page comes up. These errors may well lead you to what the problem is, as with a certain plugin. The errors displayed can also help you research the issue on the internet or in the Joomla forums.

Conflicts with extensions, components and plugins

Often you will see problems right after you install a new extension or enable a plugin. This is why it is always the best policy to backup your site's files and database frequently and before installing any new extensions. If you suspect the extension is causing the problem, uninstall it in extension manager. If you suspect the plugin, disable it. If your site is so broken that you can not get into the backend to do these steps, then restore the site from a backup.

Once the site is back to the way it was before you installed the extension or enabled the plugin, research that extension or plugin and see if there are any known issues with the settings in Joomla. Some extensions do not work with Gzip page compression turns on.

The .htaccess file

When you first install a Joomla site, you should rename the htaccess.txt file in the root of your site's files to .htaccess. This file contains many settings that are necessary for your site to run smoothly. In some cases the hosting environment will not recognize the .htaccess file in your root, and this can cause problems with your site.

Links in the menu aren't going to the right page

There can be issues with the Search Engine Friendly URLs. Turn off this feature in Global Configuration and see if the links in the menu now go to the right page. Be sure that you renamed the htaccess.txt file in the root of your site to .htaccess. There can also be a problem with your hosting environment and Search Engine Friendly URLs.

Problems with the configuration.php file

The configuration.php file that sits on the root of your site contains important information about your site. If there are errors in this file, your site will not open properly. These settings are created in the Global Configuration section of your Administrative Menu. If you can get in the backend of your site, it is best to make changes there. If you can not get into the backend, you may need to edit the configuration.php file with a text editor and upload it back to your files on the server.

With new Joomla installations, you go through a series of pages when you first initialize the site. The information that you enter on these pages are placed into the configuration.php file.

The common issues with the configuration.php file are:

public $host = ' ';  This is usually "localhost" but some hosting companies have specific names for this. Check with your hosting company before making a change.

public $user = ' '; This is the name for the database user, not the Joomla login username. They should be different. You need to set up a database before you install Joomla and make note of the database name, database username and database password. 

public $password = ' '; This is the password for the database, not the password for getting into Joomla

public $db = ' '; This is the name of the database. If you have moved your site to a different hosting company or from a local installation to a hosting server, this may need to change.

public $dbprefix = ' ';  This is the prefix for the tables in the database. If you have moved the site and database, be sure this prefix is still correct

public $live_site = 'http://... '; This is the path to the live site, the address that you would type into a web browser. If you have moved the site from a local computer or a subfolder, this can be a problem. Also check this if you have a site with https://

public $log_path = ' '; This is the path to the log folder. This must be a viable path as Joomla requires this to work properly. The log folder must also have the correct file permissions.

public $tmp_path = ' '; This is the path to the tmp folder. This must be a viable path as Joomla requires this to work properly. The tmp folder must also have the correct file permissions.

Correct file permissions

In order for Joomla to work properly, it needs to be able to access and store files in the tmp and log folders. It also needs to be able to access the configuration.php file. If these folders and file do not have the correct permissions, then Joomla will not work properly.

You can usually change the permissions for these files with an FTP program or through the file manager with your hosting company.

To check if these files are writable, go into System -> System Information ->  Directory Permissions tab. Every item on the list must have the green "Writable" icon. Scroll all the way through this list to see if there is any red "Unwritable" icons Often the log, tmp and configuration.php file are the problem. You can not change the settings here, you can just see if there is a problem.

The proper permissions for the log and tmp folders should be: 755. The correct permission for the configuration.php should be: 644 (though some people like a tighter permission level)