Scenario

I want to create a warning box (or pitfall box) that satisfies the following creteria:

1. It can be broken across pages.
2. It can contain images, displayed equations, begin{minipage}, \begin{multicols} and \lstinputlisting.
3. It occupies the whole width of the page.
4. It is enclosed by a red frame.
5. It looks like the following figure but the background color should be yellowish.

Zoomed-in View

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\documentclass{article}
\usepackage[english]{babel}
\usepackage{blindtext}

\usepackage{pifont,mdframed}

\newenvironment{warning}
{\par\begin{mdframed}[linewidth=2pt,linecolor=red]%
\begin{list}{}{\leftmargin=1cm
\labelwidth=\leftmargin}\item[\Large\ding{43}]}
{\end{list}\end{mdframed}\par}

\begin{document}
\blindtext
\begin{warning}
\blindtext
\end{warning}
\blindtext[2]
\begin{warning}
\blindtext[2]
\end{warning}

\end{document}

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thank for introducing mdframed.sty. I will figure out the other settings to make adjustments. –  xport Jan 11 '11 at 8:38

Shortcoming

1. The figure has not been vertically centered.
2. The lack of red frame.

Minimal Code

\documentclass[dvipsnames,cmyk]{article}
\usepackage[a4paper,margin=2cm]{geometry}
\usepackage{lipsum,graphicx,xcolor,framed}

\renewenvironment{leftbar}[1][\hsize]%
{%
\def\FrameCommand%
{%
\includegraphics[width=1cm]{pitfall}%
\fboxsep=\FrameSep\colorbox{cyan!5}%
}%
}%
{\endMakeFramed}

\def\dummy{bla bla bla bla bla bla bla bla bla bla bla bla bla bla.}
\begin{document}
\lipsum[1]

\begin{leftbar}[0.5\linewidth]
\noindent\dummy
$\int_a^b f(x)\,\textrm{d}x=F(b)-F(a)$
\dummy
\end{leftbar}

\lipsum[1]
\end{document}

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