Here's how to block a single image using Opera:
- left click on image you want to block: Copy Image Address
- left click somewhere on page: Block Content...
- click Details at top right, Add, ctrl+V to paste image address ... Close and Done
- refresh page and you shall see it no more
That's the simplest way to do it.
And with this post, I challenge John Bokma to explain how to do it in Firefox.