URL image in theme

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

I have firebug. But with that program it wouldn’t give the CSS solution?

No. It’s a tool that you can use to work out the CSS yourself.

ok, so it’s a CSS problem. Thanks.

But you don’t give hints? ?? (because ofcourse I already tried)

For anybody who has the same problem.

.wp-caption IMG
{
	width: auto;
	height: auto;
	max-width: 100%;
}