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HTML 

              
                <!--
  ** Style a Select Box Using Only CSS
  ** Source: http://bavotasan.com/2011/style-select-box-using-only-css/
  ** Source: http://danielneumann.com/blog/how-to-style-dropdown-with-css-only/
  ** Source: http://stackoverflow.com/a/5809186
-->

<div>
  <select>
    <option>Here is the unstyled select box</option>
    <option>The second option</option>
    <option>The third option</option>
  </select>
</div>

<hr>

<div class="styled-select slate">
  <select>
    <option>Here is the first option</option>
    <option>The second option</option>
    <option>The third option</option>
  </select>
</div>

<hr>

<div class="styled-select black rounded">
  <select>
    <option>Here is the first option</option>
    <option>The second option</option>
    <option>The third option</option>
  </select>
</div>

<div class="styled-select green rounded">
  <select>
    <option>Here is the first option</option>
    <option>The second option</option>
    <option>The third option</option>
  </select>
</div>

<div class="styled-select blue semi-square">
  <select>
    <option>Here is the first option</option>
    <option>The second option</option>
    <option>The third option</option>
  </select>
</div>

<div class="styled-select yellow rounded">
  <select>
    <option>Here is the first option</option>
    <option>The second option</option>
    <option>The third option</option>
  </select>
</div>

<hr>

<div id="mainselection">
  <select>
    <option>Select an Option</option>
    <option>Option 1</option>
    <option>Option 2</option>
  </select>
</div>

<hr>

<select id="soflow">
  <!-- This method is nice because it doesn't require extra div tags, but it also doesn't retain the style across all browsers. -->
  <option>Select an Option</option>
  <option>Option 1</option>
  <option>Option 2</option>
</select>

<select id="soflow-color">
  <!-- This method is nice because it doesn't require extra div tags, but it also doesn't retain the style across all browsers. -->
  <option>Select an Option</option>
  <option>Option 1</option>
  <option>Option 2</option>
</select>
!

CSS 

              
                /* -------------------- Page Styles (not required) */
div { margin: 20px; }

/* -------------------- Select Box Styles: bavotasan.com Method (with special adaptations by ericrasch.com) */
/* -------------------- Source: http://bavotasan.com/2011/style-select-box-using-only-css/ */
.styled-select {
   background: url(http://i62.tinypic.com/15xvbd5.png) no-repeat 96% 0;
   height: 29px;
   overflow: hidden;
   width: 240px;
}

.styled-select select {
   background: transparent;
   border: none;
   font-size: 14px;
   height: 29px;
   padding: 5px; /* If you add too much padding here, the options won't show in IE */
   width: 268px;
}

.styled-select.slate {
   background: url(http://i62.tinypic.com/2e3ybe1.jpg) no-repeat right center;
   height: 34px;
   width: 240px;
}

.styled-select.slate select {
   border: 1px solid #ccc;
   font-size: 16px;
   height: 34px;
   width: 268px;
}

/* -------------------- Rounded Corners */
.rounded {
   -webkit-border-radius: 20px;
   -moz-border-radius: 20px;
   border-radius: 20px;
}

.semi-square {
   -webkit-border-radius: 5px;
   -moz-border-radius: 5px;
   border-radius: 5px;
}

/* -------------------- Colors: Background */
.slate   { background-color: #ddd; }
.green   { background-color: #779126; }
.blue    { background-color: #3b8ec2; }
.yellow  { background-color: #eec111; }
.black   { background-color: #000; }

/* -------------------- Colors: Text */
.slate select   { color: #000; }
.green select   { color: #fff; }
.blue select    { color: #fff; }
.yellow select  { color: #000; }
.black select   { color: #fff; }


/* -------------------- Select Box Styles: danielneumann.com Method */
/* -------------------- Source: http://danielneumann.com/blog/how-to-style-dropdown-with-css-only/ */
#mainselection select {
   border: 0;
   color: #EEE;
   background: transparent;
   font-size: 20px;
   font-weight: bold;
   padding: 2px 10px;
   width: 378px;
   *width: 350px;
   *background: #58B14C;
   -webkit-appearance: none;
}

#mainselection {
   overflow:hidden;
   width:350px;
   -moz-border-radius: 9px 9px 9px 9px;
   -webkit-border-radius: 9px 9px 9px 9px;
   border-radius: 9px 9px 9px 9px;
   box-shadow: 1px 1px 11px #330033;
   background: #58B14C url("http://i62.tinypic.com/15xvbd5.png") no-repeat scroll 319px center;
}


/* -------------------- Select Box Styles: stackoverflow.com Method */
/* -------------------- Source: http://stackoverflow.com/a/5809186 */
select#soflow, select#soflow-color {
   -webkit-appearance: button;
   -webkit-border-radius: 2px;
   -webkit-box-shadow: 0px 1px 3px rgba(0, 0, 0, 0.1);
   -webkit-padding-end: 20px;
   -webkit-padding-start: 2px;
   -webkit-user-select: none;
   background-image: url(http://i62.tinypic.com/15xvbd5.png), -webkit-linear-gradient(#FAFAFA, #F4F4F4 40%, #E5E5E5);
   background-position: 97% center;
   background-repeat: no-repeat;
   border: 1px solid #AAA;
   color: #555;
   font-size: inherit;
   margin: 20px;
   overflow: hidden;
   padding: 5px 10px;
   text-overflow: ellipsis;
   white-space: nowrap;
   width: 300px;
}

select#soflow-color {
   color: #fff;
   background-image: url(http://i62.tinypic.com/15xvbd5.png), -webkit-linear-gradient(#779126, #779126 40%, #779126);
   background-color: #779126;
   -webkit-border-radius: 20px;
   -moz-border-radius: 20px;
   border-radius: 20px;
   padding-left: 15px;
}
!

JS 

              
                // No! The whole point is this is CSS-only.
// Be sure to check these in IE9/8/7... which is why I'm testing so many versions of select styles.​​​
!
999px

Console