While no website will look or behave exactly the same in every browser and on every computer or mobile device, it is a best practice to test your site in versions of the most popular standards-compliant web browsers (Firefox, Internet Explorer, Safari, and Chrome) and on mobile devices, especially following significant site revisions or addition of new material.

Many external resources that may be embedded in your site are Flash-based and therefore not readable by iPads and many other mobile devices.  Therefore, it is best to use non-Flash-based alternatives whenever possible.