Me marca error, me dice que falta width property set to 25% .
**Your code so far**
/* file: index.html */
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Photo Gallery</title>
<link rel="stylesheet" href="./styles.css">
</head>
<body>
<div class="header">
<h1>CSS FLEXBOX PHOTO GALLERY</h1>
</div>
<div id="gallery">
<img src="https://cdn.freecodecamp.org/curriculum/css-photo-gallery/1.jpg"/>
<img src="https://cdn.freecodecamp.org/curriculum/css-photo-gallery/2.jpg"/>
<img src="https://cdn.freecodecamp.org/curriculum/css-photo-gallery/3.jpg"/>
<img src="https://cdn.freecodecamp.org/curriculum/css-photo-gallery/4.jpg"/>
<img src="https://cdn.freecodecamp.org/curriculum/css-photo-gallery/5.jpg"/>
<img src="https://cdn.freecodecamp.org/curriculum/css-photo-gallery/6.jpg"/>
<img src="https://cdn.freecodecamp.org/curriculum/css-photo-gallery/7.jpg"/>
<img src="https://cdn.freecodecamp.org/curriculum/css-photo-gallery/8.jpg"/>
<img src="https://cdn.freecodecamp.org/curriculum/css-photo-gallery/9.jpg"/>
<img src="https://cdn.freecodecamp.org/curriculum/css-photo-gallery/10.jpg"/>
</div>
</body>
</html>
/* file: styles.css */
* {
box-sizing: border-box;
}
#gallery img {
width: 25%
height: 300px
}