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

Example

Wrong

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

Right

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