Pure CSS fold-down corner with transparent background
<ul>
<li><a href="#">Lorem ipsum dolor sit amet, consectetur adipisicing elit.</a></li>
</ul>ul,
li {
list-style: none;
margin: 0;
padding: 0;
}
li {
display: block;
height: 110px;
position: relative;
width: 136px;
}
li:after,
li:before {
background: blue;
content: "";
display: block;
position: absolute;
}
li:after {
height: 110px;
right: 0;
top: 0;
width: 116px;
}
li:before {
height: 90px;
left: 0;
top: 20px;
width: 20px;
}
li a {
color: #fff;
display: table-cell;
height: 110px;
position: relative;
text-align: center;
vertical-align: middle;
width: 136px;
z-index: 100;
}
li a:after {
border-color: blue;
border-style: solid;
border-width: 20px 20px 0 0;
content: "";
display: block;
left: 0;
position: absolute;
top: 0;
z-index: 1;
}
li a:hover:after { border-color: transparent red }
.lt-ie8 li {
}
.lt-ie8 li a {
background: blue;
display: block;
}