if(navigator.userAgent.indexOf("MSIE") > -1){ //Internet Explorer
document.write('<!-'+'-[if IE]>');
document.write('<input type="image" src="http://www.at-creditcard.net/img/btn_bookmark.gif" width="200" height="26" alt=""');
document.write(' onclick="window.external.AddFavorite(\'http://www.at-creditcard.net/index.html\',\'＠クレジットカード\')">');
document.write('<![endif]-'+'->');
}

else if(navigator.userAgent.indexOf("Firefox") > -1){ //Firefox
document.write('<input type="image" src="http://www.at-creditcard.net/img/btn_bookmark.gif" width="200" height="26" alt=""');
document.write(' onclick="window.sidebar.addPanel(\'＠クレジットカード\',\'http://www.at-creditcard.net/index.html\',\'\');">');
}

else if(navigator.userAgent.indexOf("Opera") > -1){ //Opera
document.write('<a href="http://www.at-creditcard.net/index.html" rel="sidebar" title="＠クレジットカード"><img src="http://www.at-creditcard.net/img/btn_bookmark.gif" width="200" height="26" alt="" /></a>');
}

else { //該当なし
void(0); //何もしない
}