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HTML 

              
                <div class="centered">
<button class="small button">Button</button>
<button class="small red button">Button</button>
<button class="small green button">Button</button>
<button class="small blue button">Button</button>

<br><br>

<button class="small button" disabled>Button</button>
<button class="small red button" disabled>Button</button>
<button class="small green button" disabled>Button</button>
<button class="small blue button" disabled>Button</button>

<br><br>

<ul class="button-group">
<li><button class="small button">Button</button></li>
<li><button class="small button">Button</button></li>
<li><button class="small button">Button</button></li>
<li><button class="small button">Button</button></li>
</ul>

<br><br><br><br>

<button class="button">Button</button>
<button class="red button">Button</button>
<button class="green button">Button</button>
<button class="blue button">Button</button>

<br><br>

<button class="button" disabled>Button</button>
<button class="red button" disabled>Button</button>
<button class="green button" disabled>Button</button>
<button class="blue button" disabled>Button</button>

<br><br>

<ul class="button-group">
<li><button class="button">Button</button></li>
<li><button class="button">Button</button></li>
<li><button class="button">Button</button></li>
<li><button class="button">Button</button></li>
</ul>

<br><br><br><br>

<button class="large button">Button</button>
<button class="large red button">Button</button>
<button class="large green button">Button</button>
<button class="large blue button">Button</button>

<br><br>

<button class="large button" disabled>Button</button>
<button class="large red button" disabled>Button</button>
<button class="large green button" disabled>Button</button>
<button class="large blue button" disabled>Button</button>

<br><br>

<ul class="button-group">
<li><button class="large button">Button</button></li>
<li><button class="large button">Button</button></li>
<li><button class="large button">Button</button></li>
<li><button class="large button">Button</button></li>
</ul>
  
  <br><br>
  
  <ul class="button-group">
<li><button class="large red button">Button</button></li>
<li><button class="large red button">Button</button></li>
<li><button class="large red button">Button</button></li>
<li><button class="large red button">Button</button></li>
</ul>
</div>
!

CSS 

              
                body{ 
    background:url(http://subtlepatterns.subtlepatterns.netdna-cdn.com/patterns/wild_oliva.png);
}
.centered {
  margin:50px auto;
  text-align:center;
}

.button::-moz-focus-inner{
  border: 0;
  padding: 0;
}

.button{
  display: inline-block;
  *display: inline;
  zoom: 1;
  padding: 6px 20px;
  margin: 0;
  cursor: pointer;
  border: 1px solid #bbb;
  overflow: visible;
  font: bold 13px arial, helvetica, sans-serif;
  text-decoration: none;
  white-space: nowrap;
  color: #555;
  
  background-color: #ddd;
  background-image: -webkit-gradient(linear, left top, left bottom, from(rgba(255,255,255,1)), to(rgba(255,255,255,0)));
  background-image: -webkit-linear-gradient(top, rgba(255,255,255,1), rgba(255,255,255,0));
  background-image: -moz-linear-gradient(top, rgba(255,255,255,1), rgba(255,255,255,0));
  background-image: -ms-linear-gradient(top, rgba(255,255,255,1), rgba(255,255,255,0));
  background-image: -o-linear-gradient(top, rgba(255,255,255,1), rgba(255,255,255,0));
  background-image: linear-gradient(top, rgba(255,255,255,1), rgba(255,255,255,0));
  
  -webkit-transition: background-color .2s ease-out;
  -moz-transition: background-color .2s ease-out;
  -ms-transition: background-color .2s ease-out;
  -o-transition: background-color .2s ease-out;
  transition: background-color .2s ease-out;
  background-clip: padding-box; /* Fix bleeding */
  -moz-border-radius: 3px;
  -webkit-border-radius: 3px;
  border-radius: 3px;
  -moz-box-shadow: 0 1px 0 rgba(0, 0, 0, .3), 0 2px 2px -1px rgba(0, 0, 0, .5), 0 1px 0 rgba(255, 255, 255, .3) inset;
  -webkit-box-shadow: 0 1px 0 rgba(0, 0, 0, .3), 0 2px 2px -1px rgba(0, 0, 0, .5), 0 1px 0 rgba(255, 255, 255, .3) inset;
  box-shadow: 0 1px 0 rgba(0, 0, 0, .3), 0 2px 2px -1px rgba(0, 0, 0, .5), 0 1px 0 rgba(255, 255, 255, .3) inset;
  text-shadow: 0 1px 0 rgba(255,255,255, .9);
  
  -webkit-touch-callout: none;
  -webkit-user-select: none;
  -khtml-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  user-select: none;
}

.button:hover{
  background-color: #eee;
  color: #555;
}

.button:active{
  background: #e9e9e9;
  position: relative;
  top: 1px;
  text-shadow: none;
  -moz-box-shadow: 0 1px 1px rgba(0, 0, 0, .3) inset;
  -webkit-box-shadow: 0 1px 1px rgba(0, 0, 0, .3) inset;
  box-shadow: 0 1px 1px rgba(0, 0, 0, .3) inset;
}

.button[disabled], .button[disabled]:hover, .button[disabled]:active{
  border-color: #eaeaea;
  background: #fafafa;
  cursor: default;
  position: static;
  color: #999;
  /* Usually, !important should be avoided but here it's really needed :) */
  -moz-box-shadow: none !important;
  -webkit-box-shadow: none !important;
  box-shadow: none !important;
  text-shadow: none !important;
}

/* Smaller buttons styles */

.button.small{
  padding: 4px 12px;
}

/* Larger buttons styles */

.button.large{
  padding: 12px 30px;
  text-transform: uppercase;
}

.button.large:active{
  top: 2px;
}

/* Colored buttons styles */

.button.green, .button.red, .button.blue {
  color: #fff;
  text-shadow: 0 1px 0 rgba(0,0,0,.2);
  
  background-image: -webkit-gradient(linear, left top, left bottom, from(rgba(255,255,255,.3)), to(rgba(255,255,255,0)));
  background-image: -webkit-linear-gradient(top, rgba(255,255,255,.3), rgba(255,255,255,0));
  background-image: -moz-linear-gradient(top, rgba(255,255,255,.3), rgba(255,255,255,0));
  background-image: -ms-linear-gradient(top, rgba(255,255,255,.3), rgba(255,255,255,0));
  background-image: -o-linear-gradient(top, rgba(255,255,255,.3), rgba(255,255,255,0));
  background-image: linear-gradient(top, rgba(255,255,255,.3), rgba(255,255,255,0));
}

/* */

.button.green{
  background-color: #57a957;
  border-color: #57a957;
}

.button.green:hover{
  background-color: #62c462;
}

.button.green:active{
  background: #57a957;
}

/* */

.button.red{
  background-color: #ca3535;
  border-color: #c43c35;
}

.button.red:hover{
  background-color: #ee5f5b;
}

.button.red:active{
  background: #c43c35;
}

/* */

.button.blue{
  background-color: #269CE9;
  border-color: #269CE9;
}

.button.blue:hover{
  background-color: #70B9E8;
}

.button.blue:active{
  background: #269CE9;
}

/* */

.green[disabled], .green[disabled]:hover, .green[disabled]:active{
  border-color: #57A957;
  background: #57A957;
  color: #D2FFD2;
}

.red[disabled], .red[disabled]:hover, .red[disabled]:active{
  border-color: #C43C35;
  background: #C43C35;
  color: #FFD3D3;
}

.blue[disabled], .blue[disabled]:hover, .blue[disabled]:active{
  border-color: #269CE9;
  background: #269CE9;
  color: #93D5FF;
}

/* Group buttons */

.button-group,
.button-group li{
  display: inline-block;
  *display: inline;
  zoom: 1;
}

.button-group{
  font-size: 0; /* Inline block elements gap - fix */
  margin: 0;
  padding: 0;
  background: rgba(0, 0, 0, .1);
  border-bottom: 1px solid rgba(0, 0, 0, .1);
  padding: 7px;
  -moz-border-radius: 7px;
  -webkit-border-radius: 7px;
  border-radius: 7px;
}

.button-group li{
  margin-right: -1px; /* Overlap each right button border */
}

.button-group .button{
  font-size: 13px; /* Set the font size, different from inherited 0 */
  -moz-border-radius: 0;
  -webkit-border-radius: 0;
  border-radius: 0;
}

.button-group .button:active{
  -moz-box-shadow: 0 0 1px rgba(0, 0, 0, .2) inset, 5px 0 5px -3px rgba(0, 0, 0, .2) inset, -5px 0 5px -3px rgba(0, 0, 0, .2) inset;
  -webkit-box-shadow: 0 0 1px rgba(0, 0, 0, .2) inset, 5px 0 5px -3px rgba(0, 0, 0, .2) inset, -5px 0 5px -3px rgba(0, 0, 0, .2) inset;
  box-shadow: 0 0 1px rgba(0, 0, 0, .2) inset, 5px 0 5px -3px rgba(0, 0, 0, .2) inset, -5px 0 5px -3px rgba(0, 0, 0, .2) inset;
}

.button-group li:first-child .button{
  -moz-border-radius: 3px 0 0 3px;
  -webkit-border-radius: 3px 0 0 3px;
  border-radius: 3px 0 0 3px;
}

.button-group li:first-child .button:active{
  -moz-box-shadow: 0 0 1px rgba(0, 0, 0, .2) inset, -5px 0 5px -3px rgba(0, 0, 0, .2) inset;
  -webkit-box-shadow: 0 0 1px rgba(0, 0, 0, .2) inset, -5px 0 5px -3px rgba(0, 0, 0, .2) inset;
  box-shadow: 0 0 1px rgba(0, 0, 0, .2) inset, -5px 0 5px -3px rgba(0, 0, 0, .2) inset;
}

.button-group li:last-child .button{
  -moz-border-radius: 0 3px 3px 0;
  -webkit-border-radius: 0 3px 3px 0;
  border-radius: 0 3px 3px 0;
}

.button-group li:last-child .button:active{
  -moz-box-shadow: 0 0 1px rgba(0, 0, 0, .2) inset, 5px 0 5px -3px rgba(0, 0, 0, .2) inset;
  -webkit-box-shadow: 0 0 1px rgba(0, 0, 0, .2) inset, 5px 0 5px -3px rgba(0, 0, 0, .2) inset;
  box-shadow: 0 0 1px rgba(0, 0, 0, .2) inset, 5px 0 5px -3px rgba(0, 0, 0, .2) inset;
}
!

JS
!
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