Только ff:
<style>
div{
background: linear-gradient(-15deg,
transparent 0,
transparent 14px,
#ddd 15px,
#ddd 100%);
width:100px;
height:100px;
position:relative;
filter:url(#f3);
resize:both;
overflow: hidden;
}
div:after{
content: "";
display:block;
background: linear-gradient(15deg,
transparent 0,
transparent 14px,
#f70 15px,
#f70 100%);
transform: rotate(-30deg);
width:58px;
height:15px;
position:absolute;
bottom:0;
right:0;
}
</style>
<svg height="0" width="0">
<defs>
<filter id="f3" x="-0.2" y="-0.2" width="200%" height="200%" >
<feOffset result="offOut" in="SourceAlpha" dx="3" dy="3" />
<feGaussianBlur result="blurOut" in="offOut" stdDeviation="3" />
<feBlend in="SourceGraphic" in2="blurOut" mode="normal" />
</filter>
</defs>
</svg>
<div contenteditable="true">div</div>
Хз как в других браузерах добиться такой же простоты.)