How to fix microdata or structured data errors in Joomla
Microdata or Structured Data was introduced in Joomla 3.3 and you can test how Google sees any page by going to the Google Structured Data Testing Tool
If you find errors in your test results, here are some ways to fix that.
Entering microdata with JCE
If you use the JCE text editor, it has microdata button in the toolbar , if you don't see it, check that it's enabled in components > JCE > editor profiles > your profile > features and layout. Enter the microdata as required then check with the structured data testing tool again.
If you are familiar with Joomla overides, then it's easy to remove the microdata that's automatically inserted by Joomla and add your own custom structured data.
(1) Override /components/com_content/views/article/tmpl/default.php
(2) Locate and remove this block
(3) Add your own custom structured data. There are various ways to prepare your own custom data, Google has some good guidelines here. From this same page, look under feature guides > content types for code examples for many types of business, e.g. local business
(4) Customise the structured data as needed, eg
(5) Add this JSON-LD data to your page either using a custom HTML module, or insert into the template itself