What is the oldest browser and shortest screen size for mobile devices that has an Internet tool and is still in use?
I am making a mobile site for older devices (not smartphones) that are still in use.
I am testing Nokia 5130 Xpress Music mobile , which is 240 x 320 pixels in size, and the browser is Opera Mini (I donโt know the version).
Is it enough to test these days, or should I check for a lower size than this and less capable browser than this?
Any suggestion?

Edit: Like on the desktop, we do not consider screen sizes below 1024 X 768 px, and we started not to consider IE6, Firefox 2 and 3.0, etc.
Are there such criteria for the screen and browser for mobile phones?
source share