<mark> tag is used to highlight text code example

Example 1: html highlight text

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;
}

Example 2: how to highlight text in html

<mark>text</mark>