An image is more expressive then words...

How you can see, the citation of a \bibitem does not go in a new line. This is my code:
\begin{thebibliography}{99}
\bibitem[Documentazione ffmpeg x x x x x x x x x x x x]{ffmpegdoc}
Descrizione progetto ffmpeg\\
\url{http://ffmpeg.org/about.html}
\end{thebibliography}
and then
\cite{ffmpegdoc}
all that "x" is just for extremes the problem
Any idea in what's the problem?