<div style="  color:#222; font-size:12px; font-family:tahoma;
  position: fixed;
  top:30px;
  left:0px;
   transform: rotate(-45deg);">
    ادعم فلسطين
</div>
<div style="  width: 0px; 
  height: 0px; 
  border-left: 0px solid transparent;
  border-right: 100px solid transparent;
  border-top: 90px solid #f00;
  position:fixed;
  top:0px;
  left:0px;
  z-index:-1;" >
  </div>