Scrollbars allow users to control content visibility. The size of the thumb indicates the amount of unseen content.
- Minimize the use of horizontal scrollbars by laying out content vertically as much as possible.
- While horizontal scrolling is unavoidable in a datagrid, strive to choose a set of default columns that minimize scrolling.
- Never use horizontal scrolling in a table of contents (as in multipage dialogs, wizards, and the third level of navigation in a tab).
- Avoid vertical scrolling of more than two pages of content. If you have more pages, consider breaking the content into separate categories or pages.
- Don't allow the scrolling of content inside other scrolling content, such that double scroll bars appear.
- Don't bury important controls in areas that scroll off the visible content area by default.