diff --git a/skin/style.css.php b/skin/style.css.php
index 5d749741b..1030a02c5 100644
--- a/skin/style.css.php
+++ b/skin/style.css.php
@@ -9,8 +9,11 @@
 		$path='../';
 	require ($path.'cis/config.inc.php');
 	//setcookie('stylesheet', DEFAULT_STYLE);
-	if (isset($_COOKIE['stylesheet']))
+	//Name des Stylesheets darf nur buchstaben von A-Z enthalten (ohne umlaute)
+	if (isset($_COOKIE['stylesheet']) && preg_match('/^[a-zA-Z]+$/', $_COOKIE['stylesheet']))
+	{
 		$stylesheet=$_COOKIE['stylesheet'];
+	}
 	else
 		$stylesheet=DEFAULT_STYLE;
 	//setcookie('stylesheet', DEFAULT_STYLE);
diff --git a/skin/styles/tw_green.css b/skin/styles/twgreen.css
similarity index 90%
rename from skin/styles/tw_green.css
rename to skin/styles/twgreen.css
index e1b943dc1..76395e3d1 100644
--- a/skin/styles/tw_green.css
+++ b/skin/styles/twgreen.css
@@ -68,13 +68,13 @@ input.TextBox
 }
 .home_logo
 {
-	background-image:url(styles/tw_green/tw_gr_logo.jpg);
+	background-image:url(styles/twgreen/tw_gr_logo.jpg);
 	width:182px;
 	height:120px;
 }
 .header_line
 {
-	background-image:url(styles/tw_green/tw_gr_header.jpg);
+	background-image:url(styles/twgreen/tw_gr_header.jpg);
 	background-repeat:repeat-x;
 	width:100%;
 	height:120px;
@@ -86,7 +86,7 @@ input.TextBox
 /* Vor IE/Mac verstecken*/
 #footer /*Menu Balken*/
 {
-	background-image:url(styles/tw_green/menu.jpg);
+	background-image:url(styles/twgreen/menu.jpg);
 	width:182px;
 	height:37px;
 	background-repeat:no-repeat;
diff --git a/skin/styles/tw_green/description.txt b/skin/styles/twgreen/description.txt
similarity index 100%
rename from skin/styles/tw_green/description.txt
rename to skin/styles/twgreen/description.txt
diff --git a/skin/styles/tw_green/menu.jpg b/skin/styles/twgreen/menu.jpg
similarity index 100%
rename from skin/styles/tw_green/menu.jpg
rename to skin/styles/twgreen/menu.jpg
diff --git a/skin/styles/tw_green/screenshot.jpg b/skin/styles/twgreen/screenshot.jpg
similarity index 100%
rename from skin/styles/tw_green/screenshot.jpg
rename to skin/styles/twgreen/screenshot.jpg
diff --git a/skin/styles/tw_green/tw_gr_header.jpg b/skin/styles/twgreen/tw_gr_header.jpg
similarity index 100%
rename from skin/styles/tw_green/tw_gr_header.jpg
rename to skin/styles/twgreen/tw_gr_header.jpg
diff --git a/skin/styles/tw_green/tw_gr_logo.jpg b/skin/styles/twgreen/tw_gr_logo.jpg
similarity index 100%
rename from skin/styles/tw_green/tw_gr_logo.jpg
rename to skin/styles/twgreen/tw_gr_logo.jpg