Border-radius

Increasing the radius leads to greater rounding

p {
    border-radius: 10px;
}

p {
    border-radius: 30px;
}

border-radius=50% makes a circle

p {
    border-radius: 50%;
}

You can specify individual values for each corner

p {
   border-top-left-radius: 15px;
   border-bottom-right-radius: 15px;
}

Round images

img {
    border: solid black 1px;
    border-radius:50%;
}