peti-peti,
I have just checked your page:
http://www.optixagency.com
The reason of problem is a conflict with your "style.css" file:
http://www.optixagency.com/wp-content/themes/optixagency4/style.css
Open it in any text editor, find the following lines:
.art-article img, img.art-article, .art-block img, .art-footer img
{
border-color: #FFFFFF;
border-style: solid;
border-width: 0;
margin: 0 10px 10px 0;
}Line "margin: 0 10px 10px 0;" causes the problem.