Bug?

When I create a new article with an image (<center><img src="http://cultura.calamo.it/img/niceimage.jpg" alt="Nice picture..."></center>) and after that I access the “edit” page to enter some new details, it adds me a new piece of code (<center><img src="http://cultura.calamo.it/img/niceimage.jpg" alt="Nice picture..."/></center>).
It happened to me that the entire page stopped working…

Thanks