var thisWeek=" "
function getWeek()
{
var cTime=new Date()
var sYear=new Date(cTime.getFullYear(),0,1)
sYear=sYear.getTime()-(sYear.getDay()-1)*(24*60*60*1000)
var cWeek=Math.ceil((cTime.getTime()-sYear)/(1*24*60*60*1000))
return(cWeek)
}

document.write("<img src='zahnarztpraxis/monat_"+ getWeek(thisWeek) +".jpg'>");

//document.write("<B> Die aktuelle Woche: </B>" + getWeek(thisWeek));