+ <p>This group of check buttons show definitions available for the video. The definition characterizes its resolution (number of pixels on horizontal and vertical). A definition is coded here, as in television systems, with a number, representing the number of vertical pixels (height), and a "p", which is an abbreviation from <a href="http://en.wikipedia.org/wiki/Progressive_scan" rel="nofollow" target="_blank"><em>progressive scan</em></a>.</p>
+ <p>The number of vertical pixels depends on the <a href="http://en.wikipedia.org/wiki/Display_aspect_ratio" rel="nofollow" target="_blank"><em>display aspect ratio</em></a> which is usually 4:3 or 16:9. Because the video needs to fit in your browser its actual size (when not in Full Screen mode) will be between 640 and 1024 horizontal pixels.</p>