Many layout problems in CSS happen because of misunderstanding the box model.
In this lesson, you will fix real problems using real code, just like developers do in real projects.
Problem
You set the width to 200 pixels, but the box looks much bigger.
This happens because padding and border are added outside the content area.
Fix
By adding box-sizing: border-box, the padding and border are included in the width.
Now the box stays exactly 200 pixels wide.
Problem
You see unwanted space between elements even though you did not add margin.
This happens because many HTML elements have default margin.
Fix
By setting margin to zero, you remove the default spacing and get full control over layout spacing.
Problem
The content does not fit inside the box and breaks the layout.
Fix
Using overflow helps keep content inside the box without breaking the design.
Developer tip
Most box model problems are solved by:
- Using box-sizing: border-box
- Resetting default margins
- Controlling overflow properly
Practice task
Create a box that:
- Has width 200px
- Padding 20px
- Border 4px solid green
First, see how big it becomes.
Then add box-sizing: border-box and fix it.
Next lesson
In the next page, you will build a practical layout using everything you learned about the CSS box model.