Bought a 5″ HDMI LCD screen for my Raspberry Pi, but it wasn’t working until I made some changes at /boot/config.txt file to force 800×480 screen resolution, edit /boot/config.txt and modify these lines:
hdmi_force_hotplug=1 hdmi_group=2 hdmi_mode=87 hdmi_cvt 800 480 60 6 0 0 0
Optionally to enable support of MJPEG, VP6, VP8, Ogg Theora & Ogg Vorbis, add these lines:
start_file=start_x.elf fixup_file=fixup_x.elf