transition in css3 using pseudo active

  .box {  
        width: 300px;  
        height: 300px;  
        background: #222;  
        -webkit-transition: width 2s ease, height 2s ease;  
        -moz-transition: width 2s ease, height 2s ease;  
        -o-transition: width 2s ease, height 2s ease;  
        -ms-transition: width 2s ease, height 2s ease;  
        transition: width 2s ease, height 2s ease;  
    }  

    .box:active
{  
        width: 500px;  
        height: 500px;  
    }