Mobile Friendly - Responsive Header/Footer Images

Example code for getting your large header / footer images to shrink in to the width of a mobile device.

If this is your current header image code:
<img src="image.jpg">

To be mobile friendly (such as on Android or an iDevice), update the style tag to this:
<img src="image.jpg" style="height:auto;max-width:100%;">

The magic is the section which has been bolded

If you have ad banners served from a third-party such as Google Adsense, update your code to their responsive ad unit
Google Adsense: