I have found that the Attribute selector fix for yahoo can be trimmed back to just body element:

body[yahoo] .hidemob1 {display:none!important;}

Now using this:

body .hidemob1 { display:none!important; }

As long as you reference your parent wrapper (ie:body) Yahoo doesnt render the media queries in webmail.

Anyone had any issues with trimming this atribute selector off to just body element?