Originally Posted by samtaleterapi
And that really leads me to the next question -
Can I actually use a responsive design, not much more advanced than the one implied here, across devices (desktop, tablet and mobile) and browsers? Does it work? Does it validate? Or does responsive web design only target a proportion of internet viewers?
It's pretty good. Typically you will place your default rendition first in the stylesheet, and if a browser doesn't support media queries, then they don't get implemented and your default rendition will apply. So you make your default something like you have now, and that's the baseline that would appear on a non-mq device. Yes it validates. Here's an example of a responsive web site that should look decent across a lot of screen sizes - http://www.ncracing.org/index.php
And the browsers that dont support the viewport meta tag, how will they behave? Do they decline gracefully or mess up my site? And if the first is the case, how do I specify which stylesheet should be used there?
They will look the same as the design made for their physical resolution. So if you had a phone size device that has 1000px across, your site will be displayed really small, and they will need to pinch-zoom to read it.
Your other option (to responsive design) is to develop separate sites for separate devices. This is what a lot of us are grateful not to need to do anymore, now that mq exists. You'd sense the device type (ie test specifically "is this an iPhone?") and then use a different stylesheet or even a completely different web page for that device. This is of course infinitely customizable, and has the advantage of being light-weight in the sense that you don't have large images that were intended for large monitors being downloaded on small devices which aren't planning on displaying them anyway. The disadvantage is of course maintenance of all the extra code.