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

Example

Wrong

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

Right

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