You can't print a specific area of a page, but you can hide the rest of the page when printing. Create a CSS that hides the element that you don't want to print:
@media print {
.someelement, .otherelement, .morelement { display: none; }
}
You can use a print style sheet, which sets the display property on everything except what you want printed to none.
You can load different stylesheets for different media using the media attribute.
style.css:
#header
{
background-color: #ccc;
font-size: 2em;
height: 4em;
clear: both;
}
print.css:
#header
{
display: none;
}
yourpage.aspx:
<head>
<link rel="stylesheet" href="style.css" type="text/css" media="screen" />
<link rel="stylesheet" href="print.css" type="text/css" media="print" />
</head>
<body>
<div id="header">My Site!</div>
<div id="content">
Only print me
</div>
</body>