My category index page shows empty spaces between subcategory images..

My category index page shows the subcategory images in 3 columns. But between some subcategory images there appear empty spaces.
When I change the admin setting to show the images in another numver of columns, the problem remains.
I'll attach a screenprint of the category index with some of the empty spaces in it.

Hope anyone can help me.

Regards.

As with most styling issues, we need to see the site live to be sure of diagnosing it correctly.

All of your subcategories are floated left as is standard, with 33% width, but there are no separators or enforced line breaks at every third element as is usual. Thus they all line up in rows, sliding as far to the left as they can. Most of your images are 231x231 px, but some are 231x232 px. The extra height sticks down and prevents the next lower div from sliding left.

How many subcategories per row do you have set?

It was the image size indeed. I resized all the images to the same size and the empty spaces all disappeared.
I set the number of images to 3 per row.

Thank you so much! Brilliant!