Irregular columns in woocommerce category& gallery pages

hello
i have a website that use wwoocommerce category for products,for show product in 4 columns, when i showing my website the product page was regular but after a time my columns showing Irregular and showing 3 product in 1 row and Fourth product show in after line ,all of column is Irregular,in other website when i choose 3column Gallery for show it,there was similary problem and show 2image in 1 row and third image show in after line.what is my website problems?
thanks!
image for this problem
http://www.axgig.com/images/29122305636645668299.jpg