Ideal viewport size for mobile phone web sites

I'm wondering which should be the ideal viewport size to design mobile web sites.

Designing a site with 320px width will speed up a lot the site in terms of images loading (as their size will be smaller), and, if just adjusting the viewport to be 320px makes it look full width, then, why should we design websites in a higher width?

• What is the disadvantage of designing a mobile website in 320px width?
• Which would you say is the ideal viewport size for a mobile website?

1. The web is inherently flexible. Embrace the medium, don't impose a false limitation because it seems easier at first.

2. What do you define as 'mobile'? Will that change in 6 or 12 months?

3. There are more devices than the iPhone. Flexible sites just work* on almost every device including the iPhone.

There many eloquent and well-informed opinions on the subject:

• http://alistapart.com/article/dao
• http://blog.andyhume.net/responsive-by-default/
• http://adactio.com/journal/6120/
• http://futurefriend.ly/

There's no harm in ruling that all images created for the site are of a specified size, although scaling and resampling them to fit their allotted container is relatively heavy work. As with anything online within the browser - a medium designed to compromise - it's a balance.