You can use the .trigger() to simulate a click on the desired tab. This is a working fiddle.
On your jquery, before the end of the document.ready :
$(".accordion .accord-header:eq(1)").trigger('click');
So your final JS :
$(document).ready(function() {
$(".accordion .accord-header").click(function() {
if($(this).next("div").is(":visible")){
$(this).next("div").slideUp("slow");
} else {
$(".accordion .accord-content").slideUp("slow");
$(this).next("div").slideToggle("slow");
}
});
$(".accordion .accord-header:eq(1)").trigger('click');
});