Even output of images

Can you tell me how to adjust the code so that the image displays horizontally instead of vertically?

I'm adding this code, but nothing changes:

.field-name-field-photo .field-item{
	float:left;
	margin-right: 10px;
	margin-bottom: 10px;

Please let me know where to add it and which specific style.css to use, as the style varies for different users. What could be the issue??? 

The website is http://grantaremont.ru/content/fotomoe