If an element has an "onmouseover" attribute, it should also have an "onfocus" attribute. This helps ensure that users who only have the keyboard can access the features as well.

Example

Wrong

<a onmouseover="alert('Hello, there');" href="#">Open an alert.</a>

Right

<a onmouseover="alert('Hello, there');" onfocus="alert('Hello, there');" href="#">Open an alert.</a>