Error 0x801901F8

Value: -2145844744 | 0x801901F8 | 2149122552

What does it mean ?

HTTP_E_STATUS_GATEWAY_TIMEOUT  
Gateway timeout (504).
Value: 504 | 0x01F8 | 0b0000000111111000

Where does it come from ?

FACILITY_HTTP  
HTTP support
Value: 25 | 0x019 | 0b00011001

Other Errors for FACILITY_HTTP