对话框气泡，总能在一些设计中给人一种清晰的感觉，在这里我们用css3技术来设计了几种对话框。

在第一个案例中，主要使用:before&:after创建两个三角形，一个和背景色一样，一个和边框色一样；在第二个案例中主要使用:before和rotate，利用旋转来达到我们需要的效果；第三个是一个倾斜的三角其实也有两种方法一个就是两个三角形叠加一个就是demo中的旋转了；第四种比较复杂，一两句说不完，还是自己看吧

demodownload

css主要代码如下：

/* demo1 */
.demo1{
    border:2px solid #ccc;
	padding:10px;
	margin-bottom:20px;
	position:relative;
	-moz-border-radius:5px;
    -webkit-border-radius:5px;
    border-radius:5px;
}
.demo1:before,.demo1:after{ 
	content:'';
	width:0;
	height:0;
	position:absolute;
}
.demo1:before{
    left:10px;
	bottom:-8px;
	border-top:8px solid #ccc;
	border-left:8px solid transparent;
	border-right:8px solid transparent;
}
.demo1:after{
    left:12px;
	bottom:-6px;
	border-top:8px solid #fff;
	border-left:6px solid transparent;
	border-right:6px solid transparent;
}
/* demo2 */
.demo2{
    border:2px solid #29B4F0;
	padding:10px;
	position:relative;
	margin-bottom:20px;
	-moz-border-radius:5px;
    -webkit-border-radius:5px;
    border-radius:5px;
}
.demo2:before{
	content:'';
	width:8px;
	height:8px;
	position:absolute;
	left:20px;
	bottom:-7px;
	background-color:#fff;
	border:2px solid #29B4F0;
	border-width: 0 2px 2px 0;
	-webkit-transform:rotate(45deg);
	-moz-transform:rotate(45deg);
	-ms-transform:rotate(45deg);
	-o-transform:rotate(45deg);
	transform:rotate(45deg);
}
/* demo3 */
.demo3{
    background-color:#B6F5FE;
	padding:10px;
	position:relative;
	margin-bottom:20px;
	-moz-border-radius:5px;
    -webkit-border-radius:5px;
    border-radius:5px;
}
.demo3:before,.demo3:after{ 
	content:'';
	width:0;
	height:0;
	position:absolute;
}
.demo3:before{
    left:10px;
	bottom:-18px;
	border-top:30px solid #B6F5FE;
	border-left:8px solid transparent;
	border-right:8px solid transparent;
	-webkit-transform:rotate(50deg);
	-moz-transform:rotate(50deg);
	-ms-transform:rotate(50deg);
	-o-transform:rotate(50deg);
	transform:rotate(50deg);
}
/* demo4 */
.demo4{
    background-color:#82AF11;
	padding:10px;
	color:#fff;
	position:relative;
	text-shadow:0 -1px 1px rgba(0,0,0,.2);
	-moz-border-radius:5px;
    -webkit-border-radius:5px;
    border-radius:5px;
}
.demo4:before{
    content:'';
	width:100px;
	height:20px;
	background-color:#82AF11;
	position:absolute;
	bottom:-20px;
	left:200px;
}
.demo4:after{
    content:'';
	width:50px;
	height:20px;
	background-color:#fff;
	position:absolute;
	bottom:-20px;
	left:200px;
	border-radius:0 20px 0 0;
}
.demo4 > :first-child:before{
     content:'';
	width:50px;
	height:20px;
	background-color:#fff;
	position:absolute;
	bottom:-20px;
	left:250px;
	border-radius:20px 0 0 0;   
}

demodownload