//Change the theme randomly every time the quote is changed
/* 
//Mozilla
.addEventListener('click',function(){change_theme();},false);
//IE6
.attachEvent('onclick',change_theme);
*/
//Easiest crossbrowser method (especially if don't need to use "this")
document.getElementById("prevBtn").onclick = function(){change_theme();};
document.getElementById("nextBtn").onclick = function(){change_theme();};