What are these dubious virus scanner pop-ups for?

On some websites, you get pop-ups telling you that your computer is infected and that you should urgently download virus scanner XYZ. What's the point of this nonsense? Why do virus scanner providers advertise in such a dubious way when you should be able to trust a virus scanner provider? Or are there third parties…

Can you unmark individual text sections/paragraphs in a word processor or web browser?

I have a really niche problem and after hours of Googling I haven't been able to find a solution. I really hope that someone here can help me. I have a partially visually impaired friend who uses a screen reader. The screen reader has the option to read only the selected text instead of the…