This video tutorial will show you how to downgrade from Wordpress 3.9 to Wordpress 3.8.3
To follow along you'll need to use an FTP program, FileZilla is recommended.
If you're using a siterubix.com domain, you can not downgrade because you don't get FTP access.
*** FileZilla WARNING *** FileZilla is a free FTP program, but it's come to me attention that when you install the software it now attempts to install other software. PLEASE DECLINE all options during the installation.
Step 1: Download an older version of wordpress to your computer and unzip/extract the zip file. http://wordpress.org/download/release-archive/
Step 2: Connect to your domain via FTP, inside HTTPDOCS you need to first delete the directory "wp-admin" and "wp-includes".
Step 3: Upload everything apart from the wp-content folder inside the HTTPDOCS folder.(as seen in video)
Step 4: Login to site and click button to update the database.
Recourses
https://my.wealthyaffiliate.com/training/ftp-filezilla-connecting-to-domain-via-ftp
https://my.wealthyaffiliate.com/training/backup-wordpress-to-dropbox-tutorial