Tumblr help - i need to make disappear my username from my post - take a look:?

[RosalieEsme]

Guys i need a little help for tumblr. When i make a post with gifs and/or graphics with a text, every time people reblog my post, there is always my username over the text (you can see an example in the picture). How can i make it go away? I've seen that some people don't have these problems with their posts, and i really don't want my username to show up every time people reblog my posts with a text.
Thank you and sorry for my english. http://i39.tinypic.com/fms4qr.png

[Charlotte]

If you click the line-arrow thing (it looks like |-> next to where you can make the text bold, etc.) , then there will just be a gray bar and your text, it should look like this picture

http://herethesilencefell.tumblr.com/post/73856037015