Editorial Style Guide and Brand Guidelines
Editorial Style Guide - U
underrepresented
One word.
underprepared
One word.
United States, U.S.
Spell out when it stands alone; use U.S. when it is a modifier (i.e., U.S. Air Force). May abbreviate after first use.
URL
Capitalize and use without periods when referring to a Universal Resource Locator, the address of a website.