diff --git a/.gitignore b/.gitignore
index 015a964b..eb5a316c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1 @@
-.classpath
-.settings
 target
diff --git a/.project b/.project
deleted file mode 100644
index e5693afd..00000000
--- a/.project
+++ /dev/null
@@ -1,23 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<projectDescription>
-	<name>acme4j</name>
-	<comment></comment>
-	<projects>
-	</projects>
-	<buildSpec>
-		<buildCommand>
-			<name>org.eclipse.jdt.core.javabuilder</name>
-			<arguments>
-			</arguments>
-		</buildCommand>
-		<buildCommand>
-			<name>org.eclipse.m2e.core.maven2Builder</name>
-			<arguments>
-			</arguments>
-		</buildCommand>
-	</buildSpec>
-	<natures>
-		<nature>org.eclipse.jdt.core.javanature</nature>
-		<nature>org.eclipse.m2e.core.maven2Nature</nature>
-	</natures>
-</projectDescription>
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 7b18a495..6fc2dc9d 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -45,3 +45,4 @@ Good programming does not end with a clean source code, but should have pretty c
 * Always give meaningful commit messages (not just "bugfix").
 * The commit message must be concise and should not exceed 50 characters. Further explanations may follow in subsequent lines, with an empty line as separator.
 * Commits must compile and must not break unit tests.
+* Do not commit IDE generated files and directories (like `.project` or `.idea`).
diff --git a/acme4j-client/.project b/acme4j-client/.project
deleted file mode 100644
index 27ef9730..00000000
--- a/acme4j-client/.project
+++ /dev/null
@@ -1,23 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<projectDescription>
-	<name>acme4j-client</name>
-	<comment></comment>
-	<projects>
-	</projects>
-	<buildSpec>
-		<buildCommand>
-			<name>org.eclipse.jdt.core.javabuilder</name>
-			<arguments>
-			</arguments>
-		</buildCommand>
-		<buildCommand>
-			<name>org.eclipse.m2e.core.maven2Builder</name>
-			<arguments>
-			</arguments>
-		</buildCommand>
-	</buildSpec>
-	<natures>
-		<nature>org.eclipse.jdt.core.javanature</nature>
-		<nature>org.eclipse.m2e.core.maven2Nature</nature>
-	</natures>
-</projectDescription>
diff --git a/acme4j-example/.project b/acme4j-example/.project
deleted file mode 100644
index f9f2fc07..00000000
--- a/acme4j-example/.project
+++ /dev/null
@@ -1,23 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<projectDescription>
-	<name>acme4j-example</name>
-	<comment></comment>
-	<projects>
-	</projects>
-	<buildSpec>
-		<buildCommand>
-			<name>org.eclipse.jdt.core.javabuilder</name>
-			<arguments>
-			</arguments>
-		</buildCommand>
-		<buildCommand>
-			<name>org.eclipse.m2e.core.maven2Builder</name>
-			<arguments>
-			</arguments>
-		</buildCommand>
-	</buildSpec>
-	<natures>
-		<nature>org.eclipse.jdt.core.javanature</nature>
-		<nature>org.eclipse.m2e.core.maven2Nature</nature>
-	</natures>
-</projectDescription>
diff --git a/acme4j-it/.project b/acme4j-it/.project
deleted file mode 100644
index 7789f73f..00000000
--- a/acme4j-it/.project
+++ /dev/null
@@ -1,23 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<projectDescription>
-	<name>acme4j-it</name>
-	<comment></comment>
-	<projects>
-	</projects>
-	<buildSpec>
-		<buildCommand>
-			<name>org.eclipse.jdt.core.javabuilder</name>
-			<arguments>
-			</arguments>
-		</buildCommand>
-		<buildCommand>
-			<name>org.eclipse.m2e.core.maven2Builder</name>
-			<arguments>
-			</arguments>
-		</buildCommand>
-	</buildSpec>
-	<natures>
-		<nature>org.eclipse.jdt.core.javanature</nature>
-		<nature>org.eclipse.m2e.core.maven2Nature</nature>
-	</natures>
-</projectDescription>
diff --git a/acme4j-utils/.project b/acme4j-utils/.project
deleted file mode 100644
index eb1e5a55..00000000
--- a/acme4j-utils/.project
+++ /dev/null
@@ -1,23 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<projectDescription>
-	<name>acme4j-utils</name>
-	<comment></comment>
-	<projects>
-	</projects>
-	<buildSpec>
-		<buildCommand>
-			<name>org.eclipse.jdt.core.javabuilder</name>
-			<arguments>
-			</arguments>
-		</buildCommand>
-		<buildCommand>
-			<name>org.eclipse.m2e.core.maven2Builder</name>
-			<arguments>
-			</arguments>
-		</buildCommand>
-	</buildSpec>
-	<natures>
-		<nature>org.eclipse.jdt.core.javanature</nature>
-		<nature>org.eclipse.m2e.core.maven2Nature</nature>
-	</natures>
-</projectDescription>