function getBrowserWidth()
{
    if (window.innerWidth)
    {
        return window.innerWidth;
    }
    else if (document.documentElement && document.documentElement.clientWidth != 0)
    {
        return document.documentElement.clientWidth;
    }
    else if (document.body)
    {
        return document.body.clientWidth;
    }
    return 0;
}

function changeClass()
{
   var theWidth = getBrowserWidth();
   var theElement = document.getElementById('main');
    if ( theWidth > 1200 )
    {
        theElement.className = 'hm1200pluss';
    }
    else if (theWidth > 1000)
    {
        theElement.className = 'hm1000pluss';
    }
    else if (theWidth > 800)
    {
        theElement.className = 'hm800pluss';
    }
    else
    {
        theElement.className = 'fallback';
    }
    return 0;
}