Image caption

Unless you post a link to your site where the problem exists, there is no way for anyone to offer much help.

https://shomidprof.wordpress.com/2012/12/20/zasto-vas-mrze-na-ask-fm-u-solved/?preview=true&preview_id=63&preview_nonce=ef992217c8

Here’s a link to my blog. Look at a image caption “Hejt.fm”

That’s being caused by the padding in this CSS:

img[class*="align"], img[class*="wp-image-"], #content .gallery .gallery-icon img {
    background-color: #FFFFFF;
    border: 1px solid #E4DFE8;
    box-shadow: 1px 1px 0 rgba(228, 223, 232, 0.5);
    padding: 6px;
}

You could either remove the padding or change the background color from white to the same color as the page background.

Where to change that? ?? sorry, im newbie.

Unfortunately that is a .com hosted site. These forums are for self hosted sites running WordPress. You might get better help from WordPress.com forums