If you have a form on your page and your visitor presses the Enter key, thinking it will move to the next field, it will actually submit the form. To prevent accidental form submission, you can disable the Enter key by using the following code in a custom header:
<script type="text/javascript">
<!-- Script courtesy of http://www.web-source.net - Your Guide to Professional Web Site Design and Development -->
function stopRKey(evt) {
   var evt = (evt) ? evt : ((event) ? event : null);
   var node = (evt.target) ? evt.target : ((evt.srcElement) ? evt.srcElement : null);
   if ((evt.keyCode == 13) && (node.type=="text")) {return false;}
}

document.onkeypress = stopRKey;
</script>