For instances wherein it is important to specify a marked text, the use of HTML5 <mark> tag is essential. This is handy for occasions wherein the author has to highlight a particular word, phrase or sentence.
The use of HTML5 <mark> tag is not present in HTML4.0 so no comparisons can be made.
When the HTML5 <mark> tag is incorporated by authors in documents, there is no issue that authors should deal with because it is compatible with the Events Attributes and Global Attributes. The work of HTML5 <mark> tag is also commendable because this is accepted by all major web browsers, specifically Safari, Opera, Google Chrome, Internet Explorer and Firefox.