If you install website_less for theme_clean or other themes, no horizontal element placement / sorting is possible. The css class oe_vertical is not added to the columns.

The Problem is in the javascript file "website.snippets.editor.js" in Line 532

var float = window.getComputedStyle(this).float;

float is undefined, but it should be left or right.

if(child_selector){

self.$wrapwrap.find(child_selector).each(function (){

var $zone = $(this);

var vertical;

var float = window.getComputedStyle(this).float;

if (float === "left" || float === "right") {

vertical = $zone.parent().outerHeight()+'px';

}

var $drop = zone_template.clone();

if (vertical) {

$drop.addClass("oe_vertical").css('height', vertical);

}

$zone.find('> *:not(.oe_drop_zone):visible').after($drop);

$zone.prepend($drop.clone());

});

}