This text has a pink background, a thin, blue left border and a thick purple bottom border. CSS lets you specify lots of things if you want.
<style type="text/css">
p {
border-width: thin ;
width: 70% ;
margin-left: 20% ;
background: pink ;
padding: 2em ;
border-left: solid ;
border-right: none ;
border-top: none ;
border-bottom: solid ;
border-left-width: thin ;
border-bottom-width: thick ;
border-left-color: blue ;
border-bottom-color: purple ;
font-size: 200% ;
}
</style>