function showPreview(width, height, href)
{
    var x = 0;
    var y = 0;
    if (navigator.appName == 'Netscape')
    {
        x = screen.availWidth;       
        y = screen.availHeight;   
    }
    else
    {
        x = screen.Width;       
        y = screen.Height;   
    }
    
    nOkno = window.open(href,'obrazek',"\'menubar = scrollbars, width="+width+",height="+height+",left="+((x-width)/2)+",top="+((y-height)/2)+"\'");

    nOkno.resizeTo(width+10, height+25);
}