Enable a element to be tab-able?

Use tabIndex. That are:

1. some elements are born to be tab-able. Such as <a>, <input> etc.
2. The sequence of tab-able elements when pressed tab is how they appear in .html file.
3. to enable an element to be tab-able, add tabIndex='0' to it.
4. to change tab-able elements' sequence. change tabIndex to 1,2,3...
5. to disable tab-able, use tabIndex = '-1'

ref: https://www.paciellogroup.com/blog/2014/08/using-the-tabindex-attribute/

Removing The Dotted Outline

https://css-tricks.com/removing-the-dotted-outline/