I am opening the left panel "300px" ,But I need to open the left panel 80% of the width . can you please tell me how to how left panel not in px in % .

I want to open panel around 80% of width.

<http://jsfiddle.net/eHded/4/>

```
.panel {
    width:300px;
    float:left;
    height:550px;
    background:#d9dada;
    position:relative;
    left:-300px;

}
.slider-arrow {
    padding:5px;
    width:10px;
    float:left;
    background:#d9dada;
    font:400 12px Arial, Helvetica, sans-serif;
    color:#000;
    text-decoration:none;
    position:relative;
    left:-300px;
}

```