If you are working with an HTML5 page, the <mark> tag can be a quick and easy way of highlighting or marking text on a page:
<mark>highlighted text</mark>
To highlight text with just HTML code and support for all browsers, set the background-color style, as shown in the example below, using the HTML tag.
<span style="background-color: #FFFF00">Yellow text.</span>
Source: computerhope.com
