var toff = 0;
var k = -181;
$(document).ready(function () {
    setTimeout('main_photo_anim()', 6000)
});

function main_photo_anim() {
    if (toff < -350) k = 181;
    if (toff > -10) k = -181;
    toff += k;
    setTimeout('main_photo_anim()', 6000);
    $(".photo_cont").animate({
        top: toff + "px"
    }, 2000)
}