Twenty Eleven theme remove white space between images

CSS- img { border: 0px; }

this didn’t work.

Your query is better asked in a CSS-specific forum.

CSS queries this specific are not within the scope of support provided by WordPress forums.

Try using Firefox with the Firebug add-on for this kind of CSS work.
https://getfirebug.com/

thanks for the suggestions, this seemed to work for me

p img, .wp-caption {
	margin-top: -0.4em;
}

The rendered HTML code shows a break tag between those images.

yes, but isn’t this normal?
I have had this
tag on other themes and it doesn’t produce the white space.