Multiple meta tags for mobile optimisation?

Question

For mobile optimization I've read that you should include all the following meta tags:

<meta name="HandheldFriendly" content="true" />
<meta name="MobileOptimized" content="320" />
<meta name="viewport" content="width=device-width">

Are they all doing slightly different things or is there a hierarchy (e.g. the later tags overwriting the previous ones)?

As MobileOptimized includes a pixel width, is it possible to use width=device-width instead and is it advisable to do so? Will something like the iPhone scale to 320px or ignore this?

Answer 1

Those tags seem to apply to Blackberry browsers and the older AvantGo browser in Palm Devices. The browsers found in iPhone (safari) and Android (including FireFox) use CSS media queries for determining which styles to apply to a web page. Since Blackberry does support them, too, I would say it is not necessary to use those meta tags and they should be considered obsolete.