To easily adjust the size of your div based on screen resolution, utilize Chrome Developer Tools.
For example, if you have a div with specific dimensions:
#bluebox {
width: 50px;
height: 50px;
background-color: blue;
}
<div id="bluebox">
</div>
However, if you only want the div to be smaller at a certain screen width, like 480px, you can use media queries:
#bluebox {
width: 50px;
height: 50px;
background-color: blue;
}
@media (max-width: 480px) {
#bluebox {
width: 25px;
height: 25px;
}
}
<div id="bluebox">
</div>
This method is accomplished through simple and standard media queries. I hope this information proves useful!