A common way to add a text highlight effect in CSS is using the background-color property.
Here is an example using inline CSS:
```
This is some highlighted text.
You can make the effect more appealing by adding some padding:
```
This is some highlighted text.
For a more defined style, you can use a class in an external or internal CSS:
```
This is some highlighted text.
You can also use an rgba value instead of a color name to set the background color visibility:
```
.highlight{
background-color: rgba(255,255,0,0.3);
padding: 8px;
}
```
This will give you a yellow highlight effect, much like a highlighter pen on paper.
