Add a ribbon to your blog

div#page::before {
z-index:9999;
position:absolute;
content: 'NO 41-bis';
font-family: Helvetica;
font-weight: bolder;
font-size: 1.4em;
width: 200px;
text-align: center;
line-height: 50px;
letter-spacing: 1px;
color: red;
transform: rotate(-45deg);
-webkit-transform: rotate(-45deg);
position: fixed;
box-shadow: 0 0 10px rgba(0,0,0,.3);
top: 25px;
right: -50px;
transform: rotate(45deg);
-webkit-transform: rotate(45deg);
background: #FFF;
z-index: 9999;
}

You have to write this in ASPETTO > PERSONALIZZA > CUSTOM CSS