function checkButtonText(id)
{
    btn = document.getElementById(id);
    if( btn.currentStyle) // IE
    {
        var p = btn.currentStyle.backgroundImage;
    }
    else var p = window.getComputedStyle(btn,null).getPropertyValue("background-image"); // non-IE
    if(p != 'none')
    {
        btn.value = '';
    }
}