Image border appearing randomly

Hello all,
I’ve noticed something screwy but cannot figure out why it is happening.

Last night when I posted an image, it blended in just fine, however, when I updayed that same image (I just changed some colours within the img) I noticed that it added a gray border behind the image by itself somehow.

I guess I am confused as to why the images are showing up with borders when a post from the previous night, with the same image file worked just fine and had no border. My css file has img border set to none.

I hope im not confusing anybody with this.

The blog is located on http://angelcrack.com/

Thank you in advance.