Check out example codes for "disable text selection html". It will help you in understanding the concepts better.

Code Example 1

<div 
 style="-moz-user-select: none;
        -webkit-user-select: none;
        -ms-user-select:none;
        user-select:none;
        -o-user-select:none;"
     
 unselectable="on"
 onselectstart="return false;" 
 onmousedown="return false;">
    Blabla
</div>

Code Example 2

-webkit-user-select: none; /* Safari */        
-moz-user-select: none; /* Firefox */
-ms-user-select: none; /* IE10+/Edge */
user-select: none; /* Standard */

Code Example 3

<div 
 style="-moz-user-select: none; -webkit-user-select: none; -ms-user-select:none; user-select:none;-o-user-select:none;" 
 unselectable="on"
 onselectstart="return false;" 
 onmousedown="return false;">
    Blabla
</div>

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