Is it possible that 0 is adding the number 0 there instead of the string with quotes around it? (Like this tabIndex="0")
<a href="https://discussions.apple.com/" tabIndex="0">Click here</a>
Not sure if you are using a framework like React but the {} look like an expression to evaluate verses a string value.
Double check what it is showing as in the browser's element inspector as well.
Topic:
App & System Services
SubTopic:
Core OS
Tags: