JSFiddle - React, Tailwind, and code Playground

HTML

<button>Clean CSS</button>
<textarea id="css">
head{
    margin:0;
    }
body {
    margin:0;
    padding:0;
    font-family: "Arial Black";
    font-size:90%;
}
body > .trex {
        margin: 10px;
    }
header, footer, section, nav, body, head{
    display:block;
}
body img{
    border:none;
}
.clearboth{
    clear:both;
}
body#redbar{
    position:fixed;
    background-color:#ef4135;
    height:5px;
    width:100%;
    z-index:999;
}
#layout{
    margin:0 auto 0 auto;
    width:1000px;
}
#layout_header{
    position:fixed;
    margin-top:5px;
    width:150px;
    float:left;
}
#layout_header h1 span{
    display:none;
}
#layout_header object{
    width:150px;
    height:112.5px;
    overflow:hidden;
}
#site_nav{
    text-transform:uppercase;
}
#site_nav ul{
    margin:0;
    padding:0;
    list-style:none;
}
#site_nav li{
    margin:5px;
    float:right;
}
#site_nav a{
    background-color:#404040;
    padding:4px 7px 4px 7px;
    color:#fff;
    text-decoration:none;
}
#site_nav a:hover, #site_nav a.selected{
    background-color:#ef4135;
}
#site_lang{
    margin-top:10px;
}
#site_lang ul{
    margin:0;
    padding:0;
    list-style:none;
}
#site_lang li{
    display:block;
    float:right;
    margin:5px;
}
#site_lang a{
    color:#000;
    font-family:Arial;
    text-decoration:none;
}
#page_wrapper{
    margin-left:180px;
    padding-top:65px;
}
#page_wrapper header{
    margin-bottom:25px;
}
#page_wrapper header h1{
    display:inline;
    clear:both;
    background-color:#404040;
    padding:4px 7px 4px 7px;
    color:#fff;
    font-size:120%;
}
#page{
    font-family: Arial, Helvetica, sans-serif;
}
#layout_footer{
    padding:30px 0 30px 0;
}
#find_close{
    display:none;
    float:right;
    margin-right:-15px;
}
#find-content{
    background-color:#fff;
    border-radius: 5px;
    -moz-border-radius: 5px;
    -webkit-border-radius: 5px;
    margin-top:10px;
}
input{
    padding:2px;
    border:#ccc solid 1px;
    border-right:#999 solid 1px;
   ...

CSS

body {
    margin:0;
    padding:0;
}

textarea, pre {
    float: left;
    overflow: auto;
    width: 400px;
    height: 300px;
    border: 1px solid #000;
}

JavaScript

$$('button')[0].addEvent('click', function(){

    var css = document.id('css').get('text');

    var newCss = css
        // replace multiple tabs or spaces by one
        .replace(/( |\t)+/g, " ")
        // remove space at beginning of line
        .replace(/(^\s)/gm, "")
        // remove body in selector lists
        .replace(/(,\s*body\s*(?={|,)|body\s*,)/gi, "")
        // remove body before {
        .replace(/(body\s*(?={))/gi, "")
        // remove rules without selector
        .replace(/[\n\r]+\{[^\}]*\}/g, "")
        // remove linebreaks
        .replace(/[\n\r]+/g, "");

    document.id('cleancss').set('text', newCss);

});