on mouseover css code example

Example 1: on hover css

/* Changes an element's color on hover */

.selector {
	background-color: black;
}

.selector:hover {
	background-color: blue;
}

Example 2: on mouseover in javascript

The mouseover event is fired at an Element when a pointing device 
(such as a mouse or trackpad) is used to move the cursor onto the 
element or one of its child elements.