taking screenshots of a paused youtube video often causes the bottom portion of your screenshot to be darker, because of youtube's horrendous decision to add extensive shading to their video scroll bar. If you install a simple extension you can add a "screenshot" button to your youtube video interface so you can take perfect screenshots no problem. Or you can just finegle things so that the video scrollbar doesn't appear when you take your screenshot, such as ending your screenshot outside of the video. Like for example, putting a text editor just at the corner of your screenshot and ending the screenshot with the mouse on the text editor, so the mouse doesn't focus the video pane and cause the scrollbar to appear
