I've faced some problems with website that is designed both for mobile devices and standard PCs (I know I can create separated websites for them, but let's not complicate that question now).
When I e.g. set the font size to 12px and width of the logo image to 200px, it looks great on PC, but it's not readable (it's very small) on (quite modern) mobile phones.
On the other hand, when I set the logo to be 40% of width, it looks good on mobile phone, but it's way too large on PC. The PC screen that I'm using hasn't much better resolution, but it's huge compared to the mobile phone's screen (10 times bigger with not more then 1.5x better resolution measured in pixels).
So, I would like my logo to be displayed as about 4x4 cm, regardless of how many pixels per centimetre has mobile device or PC screen.
Making website for PC/MAC, I know that when I will make 200/200px logo, it will be visible - it will take +/- x/y cm, no matter how big the screen is and how "good" the resolution is (there aren't so much differences). But on mobile devices it vary VERY much.
