CSS folded-corner effect

Create a simple CSS folded-corner effect without images or extra markup. It works well in all modern browsers and is best suited to designs with simple colour backgrounds.
By Nicolas Gallagher you can follow him on twitter. 


The HTML and CSS code below I pickup the red with round corner. And you can change the colour or you don't like round you can remove class rounded. Enjoy.

Demo Source

The HTML Code:

<div class="note red rounded">
    <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Mauris pulvinar rhoncus risus, vel ornare lacus sagittis sit amet. Duis vel sem magna. Proin pulvinar velit eleifend ligula ultrices vestibulum. Nunc posuere dolor eu mauris feugiat dignissim.</p>
</div>

The CSS Code:

     .note {
          position:relative;
          width:480px;
          padding:1em 1.5em;
          margin:2em auto;
          color:#fff;
          background:#97C02F;
          overflow:hidden;
      }

      .note:before {
          content:"";
          position:absolute;
          top:0;
          right:0;
          border-width:0 16px 16px 0; /* This trick side-steps a webkit bug */
          border-style:solid;
          border-color:#fff #fff #658E15 #658E15; /* A bit more verbose to work with .rounded too */
          background:#658E15; /* For when also applying a border-radius */
          display:block; width:0; /* Only for Firefox 3.0 damage limitation */
          /* Optional: shadow */
          -webkit-box-shadow:0 1px 1px rgba(0,0,0,0.3), -1px 1px 1px rgba(0,0,0,0.2);
          -moz-box-shadow:0 1px 1px rgba(0,0,0,0.3), -1px 1px 1px rgba(0,0,0,0.2);
          box-shadow:0 1px 1px rgba(0,0,0,0.3), -1px 1px 1px rgba(0,0,0,0.2);
      }

      .note.red {background:#C93213;}
      .note.red:before {border-color:#fff #fff #97010A #97010A; background:#97010A;}

 /* ROUNDED CORNERS VERSION
       * All modern browsers can produce this effect with a single pseudo-element.
       * However, they all have bugs (mainly to do with border-radius) that make this a bit tricky.
       * As far as I can tell, this is the only cross-browser method for the moment.
       * Can't use this method for the simple effect because Opera 11 will only show backgrounds
       * through transparent borders if there is a border-radius applied.
       */

      .note.rounded {
          -webkit-border-radius:5px 0 5px 5px;
          -moz-border-radius:5px 0 5px 5px;
          border-radius:5px 0 5px 5px;
      }

      .note.rounded:before {
          border-width:8px; /* Triggers a 1px 'step' along the diagonal in Safari 5 (and Chrome 10) */
          border-color:#fff #fff transparent transparent; /* Avoids the 1px 'step' in webkit. Background colour shows through */
          -webkit-border-bottom-left-radius:5px;
          -moz-border-radius:0 0 0 5px;
          border-radius:0 0 0 5px;
      }

      .note p {margin:0;}
      .note p + p {margin:1.5em 0 0;}