Check out example codes for "html text not markable". It will help you in understanding the concepts better.

Code Example 1

.unselectable {
    -webkit-touch-callout: none;
    -webkit-user-select: none;
    -khtml-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    user-select: none;
}

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