What is data-qa?

If you are someone who write selenium automation scripts, the first and probably the most painful step you go through is finding a stable, unique locator on a given UI page. Once you have found a unique locator for an element the next step is to add that locator to your page object. its a simple, repetitive however pain process. Once the scripts are written, if for any reason those locators change on the DOM, your tests may break.

To solve this issue, its best to use data-qa attributes that will be used only for automation scripts. This way even if the DOM hierarchy change, automation scripts does not need to update and your tests will be more stable.