Horizontal layout modes (masonryHorizontal, fitColumns, cellsByColumn, and straightAcross) need a container that has a height value. Be sure that your CSS has height set.
{% highlight css %}
#container {
/* either of these will work for horizontal Isotope layouts */
A **horizontal** grid layout where items are centered inside each cell. The grid is defined by two options, `columnWidth` and `rowHeight`. The horizontal equivalent of cellsByRow.
Item elements are arranged into columns. Columns progress **horizontally** from left to right. Items within those columns are arranged top-to-bottom. The horizontal equivalent of fitRows.
Item elements are arranged into rows. Rows progress **vertically** top to bottom. Similar to what you would expect from a layout that uses `float: left`.
Masonry is the default layout mode for Isotope. Item elements are arranged intelligently within a **vertical** grid. For each item element, the script calculates the next best fit for the item within the grid.
The **horizontal** equivalent of masonry layout. Instead of progressing top-to-bottom, masonryHorizontal layout will progress left-to-right. Item elements are arranged intelligently within a grid. For each item element, the script calculates the next best fit for the item within the grid.