'X' logo installed atop Twitter building, spurring San Francisco to investigate City officials say replacing letters or symbols on buildings requires a permit for design and safety reasons. The ...

The city of San Francisco has opened a complaint and launched an investigation into a giant “X” sign that was installed Friday on top of the downtown building formerly known as Twitter ...

‘X’ logo installed atop Twitter building, spurring San Francisco to investigate permit violation. Share. ... requires a permit for design and safety reasons. About the Author. Associated Press.