CSS 轮廓
1、CSS 轮廓（outline）
轮廓（outline）是绘制于元素周围的一条线，位于边框边缘的外围，可起到突出元素的作用。CSS outline 属性规定元素轮廓的样式、颜色和宽度。
2、所有CSS 轮廓（outline）属性
outline：在一个声明中设置所有的外边框属性outline-color、outline-style、outline-width、inherit
outline-color：设置外边框的颜色color-name、hex-number、rgb-number、invert、inherit
outline-style ：设置外边框的样式none、dotted、dashed、solid、double、groove、ridge、inset、outset、inherit
outline-width：设置外边框的宽度thin、medium、thick、length、inherit
<!DOCTYPE html>
<html>
<head>
<style>
p
{
border:1px solid red;
outline:green dotted thick;
}
</style>
</head>
<body>
<p><b>Note:</b> IE8 supports the outline properties only if a !DOCTYPE is
specified.</p>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<style>
p {border:1px solid red;}
p.dotted {outline-style:dotted;}
p.dashed {outline-style:dashed;}
p.solid {outline-style:solid;}
p.double {outline-style:double;}
p.groove {outline-style:groove;}
p.ridge {outline-style:ridge;}
p.inset {outline-style:inset;}
p.outset {outline-style:outset;}
</style>
</head>
<body>
<p class="dotted">A dotted outline</p>
<p class="dashed">A dashed outline</p>
<p class="solid">A solid outline</p>
<p class="double">A double outline</p>
<p class="groove">A groove outline</p>
<p class="ridge">A ridge outline</p>
<p class="inset">An inset outline</p>
<p class="outset">An outset outline</p>
<b>Note:</b> IE8 supports the outline properties only if a !DOCTYPE is
specified.
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<style>
p
{
border:1px solid red;
outline-style:dotted;
outline-color:#00ff00;
}
</style>
</head>
<body>
<p><b>Note:</b> IE8 supports the outline properties only if a !DOCTYPE is specified.</p>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<style>
p.one
{
border:1px solid red;
outline-style:solid;
outline-width:thin;
}
p.two
{
border:1px solid red;
outline-style:dotted;
outline-width:3px;
}
</style>
</head>
<body>
<p class="one">This is some text in a paragraph.</p>
<p class="two">This is some text in a paragraph.</p>
<p><b>Note:</b> IE8 supports the outline properties only if a !DOCTYPE is
specified.</p>
</body>
</html>