.round {
border-radius: 50%;
}
Take some time and fiddle with these settings to understand HOW they work.
.thumbnail{
border: 1px solid #ddd;
border-radius: 4px;
padding: 5px;
width: 150px;
}
img:hover {
opacity: 0.2;
}
Now add two different images to your HTML folder. Use the same <img> tag as before, but don't but in a height or a width - just the src and the alt
Now adjust the settings for width and opacity, try and add a border or center it
If you are feeling crazy - use this to add a separate section at the top of your website
.header {
background-color: #F1F1F1;
text-align: center;
padding: 20px;
}