One of the coolest things about the Windows Mobile ecosystem is that there’re many different devices with all shapes and forms to pick up the one that matches yours best. All those choices do’ve a dark side though, there’s a variety of screen resolution/sizes we need to make sure our Widgets work and look great on. The table shows all the supported Resolution/DPIs Windows Mobile 6.5 supports and as you can see it is a big table. For widget writing, there really’re only two options, one that we’ll call HiDPI (for 192) and then LoDPI for the rest. The reason is that, in practice, a document designed for 96 DPI (Internet Explorer on the desktop at 100%) will look fine on 96 DPI, 131 DPI and 128 DPI but it will look way too small on a 192 DPI screen. Now that we’ve reduced the supported DPIs to only two, then the best (and easiest) way to handle this in your widget is as follows: 1) Generate two CSS Style Sheets for your widget. 2) Detect the screen resolution at runtime to determine which CSS to load.
Full Article: Windows blog