The most resolution of the DELL U2717D is 1440p. That's over two times the resolution of the most frequently found video mode of 720p (which is also found on this LCD screen). In addition, this flatpanel monitor have 480i, 480p, 576i, 576p and 1080i and 1080p video modes.
This flatpanel monitor's resolution (1440p) is actually the best resolution across all flatpanel monitors that came out around the same time as the U2717D.
A 480p video mode is the worst resolution across similar types of flatpanel monitor.