Thank you for this information!
Boo-ooo! Yahoo fell down so deeply that they created a mobile version. Ugly bloated "regular" version failed to work well for mobile devices, so they opted for a separate mobile version, which is also ugly and bloated, but still "good enough" for the mobile.
That should explain you why, these days, people mostly use Google and some use less popular Bing (also bloated, but, at this moment, showing a beautiful panorama, please see), and less and less people use Yahoo.
Use laconic and clear Google as a sample, not Yahoo. Please see my past answers:
Webpage screen resolution (Cross Browser\Cross Platform) problem[
^],
To Get Screen resolution[
^].
—SA