function rotateHeader(){
	
var headerList = new Array()
headerList[0] = "http://www.sas.upenn.edu/anthro/sites/www.sas.upenn.edu.anthro/themes/abstract_studies/images/header1.jpg"
headerList[1] = "http://www.sas.upenn.edu/anthro/sites/www.sas.upenn.edu.anthro/themes/abstract_studies/images/header2.jpg" 
headerList[2] = "http://www.sas.upenn.edu/anthro/sites/www.sas.upenn.edu.anthro/themes/abstract_studies/images/header3.jpg"
headerList[3] = "http://www.sas.upenn.edu/anthro/sites/www.sas.upenn.edu.anthro/themes/abstract_studies/images/header4.jpg"
headerList[4] = "http://www.sas.upenn.edu/anthro/sites/www.sas.upenn.edu.anthro/themes/abstract_studies/images/header5.jpg"
headerList[5] = "http://www.sas.upenn.edu/anthro/sites/www.sas.upenn.edu.anthro/themes/abstract_studies/images/header6.jpg"
headerList[6] = "http://www.sas.upenn.edu/anthro/sites/www.sas.upenn.edu.anthro/themes/abstract_studies/images/header7.jpg"
headerList[7] = "http://www.sas.upenn.edu/anthro/sites/www.sas.upenn.edu.anthro/themes/abstract_studies/images/header8.jpg"
headerList[8] = "http://www.sas.upenn.edu/anthro/sites/www.sas.upenn.edu.anthro/themes/abstract_studies/images/header9.jpg"
headerList[9] = "http://www.sas.upenn.edu/anthro/sites/www.sas.upenn.edu.anthro/themes/abstract_studies/images/header11.jpg"
headerList[10] = "http://www.sas.upenn.edu/anthro/sites/www.sas.upenn.edu.anthro/themes/abstract_studies/images/header12.jpg"
headerList[11] = "http://www.sas.upenn.edu/anthro/sites/www.sas.upenn.edu.anthro/themes/abstract_studies/images/header13.jpg"
headerList[12] = "http://www.sas.upenn.edu/anthro/sites/www.sas.upenn.edu.anthro/themes/abstract_studies/images/header14.jpg"
headerList[13] = "http://www.sas.upenn.edu/anthro/sites/www.sas.upenn.edu.anthro/themes/abstract_studies/images/header15.jpg"
	
var headerImage = headerList[(Math.round(Math.random()*(headerList.length-1)))];
document.getElementById('topimage').style.backgroundImage = "url("+headerImage+")";

}