Scrollbars can be customized in CSS only on the Webkit-based browsers such as Chrome, Safari, etc. Below is the sample codes:
For scroll bar track:
```
::-webkit-scrollbar {
width: 10px;
}
```
For scroll bar handle:
```
::-webkit-scrollbar-thumb {
background: #888;
border-radius: 10px;
}
```
For the handle on hover:
```
::-webkit-scrollbar-thumb:hover {
background: #555;
}
```
Unfortunately, as of now, there’s no standard way to style the scrollbar across all browsers with CSS. Mozilla Firefox, Internet Explorer and Microsoft Edge do not support scrollbar styling.
For wider browser support, you may need to use JavaScript plugins or libraries like Perfect Scrollbar, Simplebar, etc.
