Check out example codes for "css text highlight". It will help you in understanding the concepts better.

Code Example 1

/*Term: css text highlight*/

/*This uses the element ::selection, which is as far as i
know only supported by Google Chrome so far. This is not
a problem though, since other browsers will simply keep
the regular highliting styles.*/

/*Example*/
::selection {
  background-color: #000; /*Highlight Color*/
  color: #fff; /*Text Color*/
}

Code Example 2

<body>
<p>The Math test is on <mark>Friday</mark>.</p>
</body>

Code Example 3

For HTML5: (with 'mark' tag)

<p>Do not forget to buy <mark>milk</mark> today.</p> 

In CSS file: (To customize highlight)

mark {
  background-color: yellow;
  color: black;
}

Code Example 4

<style>
mark { 
  background-color: yellow;
  color: black;
}
</style>

<mark>Highlighted text!!</mark>

Code Example 5

mark {
  display: inline-block;
  line-height: 0em;
  padding-bottom: 0.5em;
}

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