Over time, the scroll bar on the right hand side of the books I have been reading become populated with horizontal lines/links to various sections of the book's text, which generate a pop-up of the text when moused-over.
1.) What causes these lines/link to be created?
2.) What is the purpose of this lines/links feature?
3.) How do I turn this feature on and off?
4.) Anything more that I need to know about this feature?
Thanks for your help.
