diff --git a/doc/developer/introduction.tex b/doc/developer/introduction.tex
index 54c1ae77b185aa607ac5a7c1815ecb8c02961f1a..b19747d9410c7c05624f397b2074fe6c8302c8a6 100644
--- a/doc/developer/introduction.tex
+++ b/doc/developer/introduction.tex
@@ -58,7 +58,7 @@ in the index corresponds to an actual \framac value.
 
 
 \begin{important}
-  The most important paragraphs are displayed inside gray boxes like this one.
+  The most important paragraphs are displayed inside orange boxes like this one.
   A plug-in developer \textbf{must} follow them very carefully.
 \end{important}
 
diff --git a/doc/developer/macros.sty b/doc/developer/macros.sty
index f53b62d4f33553a62518435393d6ce851be7c1da..dc0bc789d544df3f5074828a114e989968018fe6 100644
--- a/doc/developer/macros.sty
+++ b/doc/developer/macros.sty
@@ -93,13 +93,6 @@
 \font\manual=manfnt
 \def\dbend{{\manual\char127}}
 
-%\newlength{\longueur}
-\newenvironment{important}%
-{\hspace{5pt plus \linewidth minus \marginparsep}%
- \begin{lrbox}{\@tempboxa}%
-   \begin{minipage}{\linewidth - 2\fboxsep}}
-{\end{minipage}\end{lrbox}\colorbox{gris}{\usebox{\@tempboxa}}}
-
 \newtheorem{convention}{Recommendation}[chapter]
 \newtheorem{myexample}{Example}[chapter]
 
diff --git a/doc/eva/main.tex b/doc/eva/main.tex
index c775e3f44be17ad384bd0ea4f142df07b7967a38..20057ec1d9c6f2b3abad48c1f330d3542f24a223 100644
--- a/doc/eva/main.tex
+++ b/doc/eva/main.tex
@@ -21,13 +21,6 @@
 \newcommand{\cbopen}{\mbox{\tt \{}}
 \newcommand{\cbclose}{\mbox{\tt \}}}
 
-% Special environment
-\definecolor{gris}{gray}{0.85}
-
-\makeatletter
-\newenvironment{important}{\begin{colbox}{gris}}{\end{colbox}}
-\makeatother
-
 \newcommand{\framacversion}%
            {\input{../../VERSION} (\input{../../VERSION_CODENAME}\unskip)}
 \newcommand{\isoc}{\textsf{C99}}
diff --git a/doc/frama-c-book.cls b/doc/frama-c-book.cls
index 7aa4f114a01e35e06542d9449383c2f8dca4139d..1b83e92b0fbc4f5556fd93dd61847403590cbb96 100644
--- a/doc/frama-c-book.cls
+++ b/doc/frama-c-book.cls
@@ -382,7 +382,7 @@
   \end{center}
 }
 
-\newenvironment{warning}{\begin{colbox}{frama-c-dark-orange!30}}{\end{colbox}}
+\newenvironment{important}{\begin{colbox}{frama-c-dark-orange!30}}{\end{colbox}}
 \newenvironment{information}{\begin{colbox}{frama-c-green!30}}{\end{colbox}}
 
 % --------------------------------------------------------------------------
diff --git a/doc/userman/macros.tex b/doc/userman/macros.tex
index 97b84a5b5dc1ad82022e6447f7429c999ca7903e..d5300326348d5f0b2c2d34126ed4d391bfa29726 100644
--- a/doc/userman/macros.tex
+++ b/doc/userman/macros.tex
@@ -43,12 +43,4 @@
 % Special environment
 \definecolor{gris}{gray}{0.85}
 
-\makeatletter
-\newenvironment{important}%
-{\hspace{5pt plus \linewidth minus \marginparsep}%
- \begin{lrbox}{\@tempboxa}%
-   \begin{minipage}{\linewidth - 2\fboxsep}}
-{\end{minipage}\end{lrbox}\colorbox{gris}{\usebox{\@tempboxa}}}
-\makeatother
-
 \newtheorem{convention}{Recommendation}[chapter]
diff --git a/src/plugins/e-acsl/doc/userman/macros.tex b/src/plugins/e-acsl/doc/userman/macros.tex
index 513101b9c92ffb8c0f8d08c3d0b9c41e1dd2c58f..212365b7a111053a983228da87649b6f6f991e29 100644
--- a/src/plugins/e-acsl/doc/userman/macros.tex
+++ b/src/plugins/e-acsl/doc/userman/macros.tex
@@ -288,9 +288,3 @@ evolve in the future and/or not work as expected.}}
 \newcommand{\B}[1]{\textbf{#1}}
 
 \definecolor{gris}{gray}{0.85}
-\makeatletter
-\newenvironment{important}%
-{\hspace{5pt plus \linewidth minus \marginparsep}%
- \begin{lrbox}{\@tempboxa}%
-   \begin{minipage}{\linewidth - 2\fboxsep}}
-{\end{minipage}\end{lrbox}\colorbox{gris}{\usebox{\@tempboxa}}}