Clip is used a lot in JS for animations where you can just change the co-ordinates dynamically and have the image appear to move in any direction as required. It can of course be done by other means but is the most efficient and simplest way of doing something like that.
Clip was the answer to a quiz I posted last year and was used to produce this effect.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Untitled Document</title>
<style type="text/css">
* {
margin:0;
padding:0
}
.outer {
position:relative;
width:60%;
margin:20px auto;
font-size:124%;
min-width:400px;
}
p {
position:absolute;
top:0;
left:0;
width:100%;
padding:10px;
background:#fcc;
color:red;
border:10px solid;
}
p.tl{
background:red;
color:green;
clip:rect(0 150px 200px 0);
}
p.tr {
background:yellow;
color:#000;
clip:rect(0 auto 100px 150px);
}
p.bl {
background:blue;
color:yellow;
clip:rect(200px 350px auto 0);
}
p.br {
background:teal;
color:orange;
clip:rect(100px auto auto 350px);
}
</style>
</head>
<body>
<div class="outer">
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Morbi mi. Nullam ullamcorper accumsan nisi. Nulla scelerisque, ipsum id ultricies tempor, lorem ipsum dignissim nibh, semper sagittis nisi elit vel nulla. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Mauris quam tellus, imperdiet id, fringilla quis, rhoncus quis, enim. Cras ornare. Etiam congue. Nulla facilisi. In sagittis, massa quis mollis imperdiet, tellus mauris vulputate nisi, eu auctor orci mi eget nisl. Donec nec nibh. Nulla sit amet nulla in eros scelerisque scelerisque. Vivamus id risus. Vestibulum ante ipsum primis in faucibus orci luctus et ultrices posuere cubilia Curae; Duis varius, tellus eget bibendum porta, lacus augue bibendum pede, vel aliquet purus massa nec libero. Mauris sagittis accumsan sem. Aenean vel ante. </p>
<p class="tl">Lorem ipsum dolor sit amet, consectetur adipiscing elit. Morbi mi. Nullam ullamcorper accumsan nisi. Nulla scelerisque, ipsum id ultricies tempor, lorem ipsum dignissim nibh, semper sagittis nisi elit vel nulla. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Mauris quam tellus, imperdiet id, fringilla quis, rhoncus quis, enim. Cras ornare. Etiam congue. Nulla facilisi. In sagittis, massa quis mollis imperdiet, tellus mauris vulputate nisi, eu auctor orci mi eget nisl. Donec nec nibh. Nulla sit amet nulla in eros scelerisque scelerisque. Vivamus id risus. Vestibulum ante ipsum primis in faucibus orci luctus et ultrices posuere cubilia Curae; Duis varius, tellus eget bibendum porta, lacus augue bibendum pede, vel aliquet purus massa nec libero. Mauris sagittis accumsan sem. Aenean vel ante. </p>
<p class="tr">Lorem ipsum dolor sit amet, consectetur adipiscing elit. Morbi mi. Nullam ullamcorper accumsan nisi. Nulla scelerisque, ipsum id ultricies tempor, lorem ipsum dignissim nibh, semper sagittis nisi elit vel nulla. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Mauris quam tellus, imperdiet id, fringilla quis, rhoncus quis, enim. Cras ornare. Etiam congue. Nulla facilisi. In sagittis, massa quis mollis imperdiet, tellus mauris vulputate nisi, eu auctor orci mi eget nisl. Donec nec nibh. Nulla sit amet nulla in eros scelerisque scelerisque. Vivamus id risus. Vestibulum ante ipsum primis in faucibus orci luctus et ultrices posuere cubilia Curae; Duis varius, tellus eget bibendum porta, lacus augue bibendum pede, vel aliquet purus massa nec libero. Mauris sagittis accumsan sem. Aenean vel ante. </p>
<p class="bl">Lorem ipsum dolor sit amet, consectetur adipiscing elit. Morbi mi. Nullam ullamcorper accumsan nisi. Nulla scelerisque, ipsum id ultricies tempor, lorem ipsum dignissim nibh, semper sagittis nisi elit vel nulla. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Mauris quam tellus, imperdiet id, fringilla quis, rhoncus quis, enim. Cras ornare. Etiam congue. Nulla facilisi. In sagittis, massa quis mollis imperdiet, tellus mauris vulputate nisi, eu auctor orci mi eget nisl. Donec nec nibh. Nulla sit amet nulla in eros scelerisque scelerisque. Vivamus id risus. Vestibulum ante ipsum primis in faucibus orci luctus et ultrices posuere cubilia Curae; Duis varius, tellus eget bibendum porta, lacus augue bibendum pede, vel aliquet purus massa nec libero. Mauris sagittis accumsan sem. Aenean vel ante. </p>
<p class="br">Lorem ipsum dolor sit amet, consectetur adipiscing elit. Morbi mi. Nullam ullamcorper accumsan nisi. Nulla scelerisque, ipsum id ultricies tempor, lorem ipsum dignissim nibh, semper sagittis nisi elit vel nulla. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Mauris quam tellus, imperdiet id, fringilla quis, rhoncus quis, enim. Cras ornare. Etiam congue. Nulla facilisi. In sagittis, massa quis mollis imperdiet, tellus mauris vulputate nisi, eu auctor orci mi eget nisl. Donec nec nibh. Nulla sit amet nulla in eros scelerisque scelerisque. Vivamus id risus. Vestibulum ante ipsum primis in faucibus orci luctus et ultrices posuere cubilia Curae; Duis varius, tellus eget bibendum porta, lacus augue bibendum pede, vel aliquet purus massa nec libero. Mauris sagittis accumsan sem. Aenean vel ante. </p>
</div>
</body>
</html>
It could be done by other means (overflow:hidden and absolute positioning sections into place) but clip was easier in this case and works well even for a fluid example as shown above.
There are many css properties (methods) that can do the same thing and the one you use depends on the job in hand and which is easiest and most economical.
Possibly in the future clip may be able to make shapes rather than rectangles which will be much more interesting. At present you can imitate clip in most cases by other means without much extra code so it is a bit of a wasted property in some respects.