The best CSS rounded corners method

I love this example :

Even More CSS Roudned Corners 2

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Basic Example

The HTML is simple

<div class="dialog"><div class="content"><div class="t"></div>
  <!-- Your content goes here -->
</div><div class="b"><div></div></div></div>

The Css is excellent

/* 
  -- Even more rounded corners with CSS: Base stylesheet --
*/

.dialog {
 position:relative;
 margin:0px auto;
 min-width:8em;
 max-width:760px; /* based on image dimensions - not quite consistent with drip styles yet */
 color:#fff;
 z-index:1;
 margin-left:12px; /* default, width of left corner */
 margin-bottom:0.5em; /* spacing under dialog */
}

.dialog .content,
.dialog .t,
.dialog .b,
.dialog .b div {
 background:transparent url(dialog2-blue-800x1600.png) no-repeat top right;
 _background-image:url(dialog2-blue.gif);
}

.dialog .content {
 position:relative;
 zoom:1;
 _overflow-y:hidden;
 padding:0px 12px 0px 0px;
}

.dialog .t {
 /* top+left vertical slice */
 position:absolute;
 left:0px;
 top:0px;
 width:12px; /* top slice width */
 margin-left:-12px;
 height:100%;
 _height:1600px; /* arbitrary long height, IE 6 */
 background-position:top left;
}

.dialog .b {
 /* bottom */
 position:relative;
 width:100%;
}

.dialog .b,
.dialog .b div {
 height:30px; /* height of bottom cap/shade */
 font-size:1px;
}

.dialog .b {
 background-position:bottom right;
}

.dialog .b div {
 position:relative;
 width:12px; /* bottom corner width */
 margin-left:-12px;
 background-position:bottom left;
}

.dialog .hd,
.dialog .bd,
.dialog .ft {
 position:relative;
}

.dialog .wrapper {
 /* extra content protector - preventing vertical overflow (past background) */
 position:static;
 max-height:1000px;
 overflow:auto; /* note that overflow:auto causes a rather annoying 
              redraw "lag" in Firefox 2, and may degrade performance. 
              Might be worth trying without if you aren't worried about 
              height/overflow issues. */
}

.dialog h1,
.dialog p {
 margin:0px; /* margins will blow out backgrounds, leaving whitespace. */
 padding:0.5em 0px 0.5em 0px;
}

.dialog h1 {
 padding-bottom:0px;
}