Hovering and Mobiles
One action that touch-screen devices have difficulty with, but devices with mice or trackpads find natural, is hovering -- leaving the mouse pointer over something without clicking on it. Several smartphone browsers simply do not have the concept.
One could abandon hovering completely, for it is far from essential in web site design. However, if one is tempted to use it, then one must ensure that non-hovering alternatives are provided. In the example below, those who cannot hover can click on the menu heading to be taken to a page (with non-recommended wording) which will present the same links that hoverers would see.