Hide sidebar or show small side bar for web app

1. How big should a sidebar be?
2. What is a sidebar on a website?

How big should a sidebar be?

Width and Height of the Sidebar

A width between 20% and 40% is usually the best choice for a single sidebar and if you're going to use more than one sidebar, I suggest you don't exceed a total width of 50% (20% + 20% and 15% + 35%, for example).

What is a sidebar on a website?

Definitions. The sidebar navigation is the vertical list of links in the left panel of some webpages. Microsite webpages are required to have sidebar navigation, except the homepage and pages using the wide template.