【html(直接css)】
<div style="margin:10px;box-shadow:2px 3px 5px rgba(0,0,0,.3);border-style:solid;border-width:5px;border-color:#fd3 #d92 #b72 #d92;background:#fb3;padding:5px;"><div style="border-style:solid;border-width:3px;border-color:#b72 #d92 #fd3 #d92;background:#fb3;padding:5px;"><div style="border-style:solid;border-width:2px;border-color:#b72 #d92 #fd3 #d92;background:#fb3;padding:3px;"><div style="border:solid 1px #d92;background-color:#ffd;padding:10px;box-shadow:0px 0px 10px rgba(0,0,0,.3) inset;color:#630;">枠内の文字</div></div></div></div>