resize image proportionally

by Luiz Silva

HTML

<p>Grande</p>
<img class="original" src="https://www.google.com.br/images/srpr/logo11w.png"/>
<p>MĂ©dio</p>
<img class="medium" src="https://www.google.com.br/images/srpr/logo11w.png"/>
<p>Pequeno</p>
<img class="small" src="https://www.google.com.br/images/srpr/logo11w.png"/>

CSS

.original {
    width: 100%;
    height: auto;
}
.medium {
    width: 240px;
    height: auto;
}
.small {
    width: 120px;
    height: auto;
}