How usable are bars that disappear / reappear on scroll?

1. What do I do if my scroll bar disappears?
2. How do you slide down a bar on scroll?

What do I do if my scroll bar disappears?

Click Start > Settings. Under Windows Settings, scroll down, and then click Ease of Access > Display. Scroll down, and then set Automatically hide scroll bars in Windows to Off.

How do you slide down a bar on scroll?

To create a slide down navigation bar you need to use HTML, CSS, and JavaScript. HTML will make the structure of the body, CSS will make it looks good. This kind of sliding navbar looks attractive on a site. By using JavaScript you can easily make the navigation bar slideable when the user scrolls down.