Question

I am trying to create a header with a image which responds to screen size like one: http://appex.no/referanser

Any ideas on how they did it?

Answer 1

<div id="banner" style="width:auto;overflow:hidden;">
<img src="..." style="width:100%;" />
</div>

should work; then the div stays auto for responsive layouts and the img takes the size of the parent div

they removed the image with something like:

@media handheld, only screen and (max-width: 400px){ 
   div#banner { display:none; 
}

(just used inline for sake of the demonstration but can be class of course)