However, not everybody needs all those features. If you're looking for simple CSS framework, let me introduce Vital to you. Vital is built to be lightweight and flexible, as a result, many web application can use it as a backbone CSS.
Here're some of the components in Vital CSS framework
It's bundled with a CSS grid. You can either specifiy the columns you need or using the Automatic Grid - it will assume you want equally sized column. It lacks of grid preference for different viewports, something Bootstrap has.
A standard UI for notification.
A few size, shape and fill options for buttons.
To ensure cross platform consistency, form is all styled up to appear identically across different browsers.
You will also get Navigation Header, Tables, Pagination, Tab, Font Icons, Loaders and Typography.