Wordpress just released WP 4.0 and Joomla 3.x is in a constant upgrade cycle. They both are promoting one click upgrades that you can do yourself.
This is just not true for anything other than the most basic websites.
As there was a huge initiative by the organizations behind these CMS system to upgrade this week, our phone is ringing non-stop as website owners are crashing their websites.
There really is a process that must be followed.
1) check for server compatibity. Will the servers PHP and mySQL support the new version of the CMS
2) check all plugins and extensions. Are they compatible with the new version
3) check the template for compatibility
4) if your site customized in any way, those customization may have to be done over
And then, if all of this checks, upgrade a work copy of the site. DO NOT UPGRADE A LIVE WEBSITE!!
Best is to call us.
Let us know if we can help