This code only writes the link if IE browser:
              <SCRIPT language=JavaScript>
                <!--
                var agt=navigator.userAgent.toLowerCase(); 
                var is_aol = (agt.indexOf("aol") != -1);
                if (navigator.appName=='Microsoft Internet Explorer' && 
                is_aol==false) {
                document.write('Don\'t forget to print this page and to <A 
                href="javascript:AddBookmark()">bookmark</A> 
                this site.');
                }
                else if (navigator.appName=='Netscape') {
                document.write('Don\'t forget to print this page.') 
                }
                else {
                document.write('Don\'t forget to print this page.')
                }
                //-->
                </SCRIPT>
              
              This code goes in the head.
              <SCRIPT language=JavaScript>
                <!--
                var url = "http://www.digitalwidgets.com"
                var name = "Digital Widgets"
                function AddBookmark() {
                window.external.AddFavorite(url, name)
                }
                //-->
                </SCRIPT>