Photos are aligned on Macs but not on PCs

On my website I’ve created a page with rows of images with text underneath each picture. Each image and its accompanying text represents an article link. On my Mac I arranged these columns of images to be perfectly aligned, but on PCs they are all staggered in places. Can I fix this – perhaps in HTML? Also I have a Photocrati photographers’ theme – not sure if that makes a difference. Thanks!