LaTeX.org

Hi,
Recently, I create a graph by tikz package. But my content is not visible anymore. Is anyone can help me?
Thanks very much.

Here is the source file: (my contend "Hello world" is missing)

\documentclass{article}
\usepackage{tikz}
%%%<
\usepackage{verbatim}
\usepackage[active,tightpage]{preview ...