function startScreen(theURL) {
  window.open(theURL,'Screen','scrollbars=yes,resizable=yes,width=638,height=440');

}
function startShow(theURL) {
  window.open(theURL,'slide','scrollbars=yes,resizable=yes,width=638,height=440');

}


function endShow() {

//write code to close the window and bring focus to the main page

}