Index: t3lib/class.t3lib_compressor.php
===================================================================
--- t3lib/class.t3lib_compressor.php	(Revision 7483)
+++ t3lib/class.t3lib_compressor.php	(Arbeitskopie)
@@ -66,13 +66,20 @@
 				// we remove BACK_PATH from $filename, so make it relative to TYPO3_mainDir
 			$filenameFromMainDir = substr($filename, strlen($GLOBALS['BACK_PATH']));
 				// if $options['baseDirectories'] set, we only include files below these directroies
-			if (!isset($options['baseDirectories']) || $this->checkBaseDirectory($filenameFromMainDir, $options['baseDirectories'])) {
+			if ((
+					!isset($options['baseDirectories']) 
+					|| $this->checkBaseDirectory($filenameFromMainDir, array_merge($options['baseDirectories'], array($this->targetDirectory)))
+				) && (
+					$fileOptions['media'] === 'all'
+				)
+			)
+			 {
 				$filesToInclude[] = $filenameFromMainDir;
 					// remove the file from the incoming file array
 				unset($cssFiles[$filename]);
 			}
 		}
-
+		
 		if (count($filesToInclude)) {
 			$targetFile = $this->createMergedCssFile($filesToInclude);
 			$concatenatedOptions = array(
@@ -100,27 +107,147 @@
 		$unique = '';
 
 		foreach ($filesToInclude as $filename) {
-			$unique .= $filename . filemtime($GLOBALS['BACK_PATH'] . $filename) . filesize($GLOBALS['BACK_PATH'] . $filename);
+			$unique .= $filename . 
+				filemtime(t3lib_div::resolveBackPath(PATH_typo3 . $filename)) . 
+				filesize(t3lib_div::resolveBackPath(PATH_typo3 . $filename));
 		}
 		$targetFile = $this->targetDirectory . TYPO3_MODE . '-'. md5($unique) . '.css';
 
 			// if the file doesn't already exist, we create it
-		if (!file_exists($targetFile)) {
+		if (!file_exists(PATH_site . $targetFile)) {
 			$concatenated = '';
 				// concatenate all the files together
 			foreach ($filesToInclude as $filename) {
-				$contents = file_get_contents($GLOBALS['BACK_PATH'] . $filename);
-				$concatenated .= $this->cssFixRelativeUrlPaths($contents, dirname($filename) . '/', $this->targetDirectory);
+				$contents = t3lib_div::getUrl(t3lib_div::resolveBackPath(PATH_typo3 . $filename));
+					// only fix paths if files aren't compressed already (and therefore fixed)
+				if(!is_int(strpos($filename, $this->targetDirectory))) {
+					$concatenated .= $this->cssFixRelativeUrlPaths($contents, dirname($filename) . '/');
+				} else {
+					$concatenated .= $contents;
+				}
 			}
+			t3lib_div::writeFile(PATH_site . $targetFile, $concatenated);
 
-			if (strlen($concatenated)) {
-				t3lib_div::writeFile(PATH_site . $targetFile, $concatenated);
+		}
+		return $targetFile;
+	}
+	
+	/**
+	 * Compress multiple css files
+	 * 
+	 * @param array $cssFiles	The files to compress (array key = filename)
+	 * @param array $options	Additional options
+	 * @return array 			The CSS files after compression (array key = new filename)
+	 */
+	public function compressCssFiles(array $cssFiles, $options) {
+		$filesCompressed = array();
+		$leaveUncompressed = array();
+		foreach ($cssFiles as $filename => $fileOptions) {
+				// we remove BACK_PATH from $filename, so make it relative to TYPO3_mainDir
+			$filenameFromMainDir = substr($filename, strlen($GLOBALS['BACK_PATH']));
+				// if $options['baseDirectories'] set, we only include files below these directroies
+			if (!isset($options['baseDirectories']) 
+				|| $this->checkBaseDirectory($filenameFromMainDir, array_merge($options['baseDirectories'], array($this->targetDirectory)))
+			) {
+				$filesCompressed[$GLOBALS['BACK_PATH'] . '../' . $this->compressCssFile($filename)] = $fileOptions;
+					// remove the file from the incoming file array
+				unset($cssFiles[$filename]);
+			} else {
+					// leave files not in the stylesheet directories uncompressed
+				$leaveUncompressed[$filename] = $fileOptions;
 			}
 		}
+		return array_merge($filesCompressed, $leaveUncompressed);
+	}
+
+	/**
+	 * Compresses a CSS file
+	 * 
+	 * Options:
+	 *   baseDirectories		If set, only include files below one of the base directories
+	 *
+	 * removes comments and whitespaces
+	 * Adopted from http://drupal.org/files/issues/minify_css.php__1.txt
+	 *
+	 * @param	string	$filename		Source filename
+	 * @return	string		Filename of the compressed file
+	 */
+	public function compressCssFile($filename) {
+			// generate the unique name of the file
+		$filenameFromMainDir = substr($filename, strlen($GLOBALS['BACK_PATH']));
+		$unique = $filenameFromMainDir . filemtime($filename) . filesize($filename);
+		$targetFile = $this->targetDirectory . TYPO3_MODE . '-compressed-' . md5($unique) . '.css';
+			// only create it, if it doesn't exist, yet
+		if (!file_exists(PATH_site . $targetFile)) {
+			$contents = t3lib_div::getUrl(t3lib_div::resolveBackPath(PATH_typo3 . $filename));
+				// Perform some safe CSS optimizations.
+			$contents = str_replace("\r", '', $contents);  // Strip any and all carriage returns.
+				// Match and process strings, comments and everything else, one chunk at a time.
+				// To understand this regex, read: "Mastering Regular Expressions 3rd Edition" chapter 6.
+			$contents = preg_replace_callback('%
+				# One-regex-to-rule-them-all! - version: 20100220_0100
+				# Group 1: Match a double quoted string.
+				("[^"\\\\]*+(?:\\\\.[^"\\\\]*+)*+") |  # or...
+				# Group 2: Match a single quoted string.
+				(\'[^\'\\\\]*+(?:\\\\.[^\'\\\\]*+)*+\') |  # or...
+				# Group 3: Match a regular non-MacIE5-hack comment.
+				(/\*[^\\\\*]*+\*++(?:[^\\\\*/][^\\\\*]*+\*++)*+/) |  # or...
+				# Group 4: Match a MacIE5-type1 comment.
+				(/\*(?:[^*\\\\]*+\**+(?!/))*+\\\\[^*]*+\*++(?:[^*/][^*]*+\*++)*+/(?<!\\\\\*/)) |  # or...
+				# Group 5: Match a MacIE5-type2 comment.
+				(/\*[^*]*\*+(?:[^/*][^*]*\*+)*/(?<=\\\\\*/))  # folllowed by...
+				# Group 6: Match everything up to final closing regular comment
+				([^/]*+(?:(?!\*)/[^/]*+)*?)
+				# Group 7: Match final closing regular comment
+				(/\*[^/]++(?:(?<!\*)/(?!\*)[^/]*+)*+/(?<=(?<!\\\\)\*/)) |  # or...
+				# Group 8: Match regular non-string, non-comment text.
+				([^"\'/]*+(?:(?!/\*)/[^"\'/]*+)*+)
+				%Ssx', array('self','compressCssPregCallback'), $contents); // Do it!
+			$contents = preg_replace('/^\s++/', '', $contents);				 // Strip leading whitespace.
+			$contents = preg_replace('/[ \t]*+\n\s*+/S', "\n", $contents);  // Consolidate multi-lines space.
+			$contents = preg_replace('/(?<!\s)\s*+$/S', "\n", $contents);   // Ensure file ends in newline.
+			$contents = $this->cssFixRelativeUrlPaths($contents, dirname($filename) . '/');
+			
+			t3lib_div::writeFile(PATH_site . $targetFile, $contents);
+		}
 		return $targetFile;
 	}
 
 	/**
+	 * Callback function for preg_replace
+	 * 
+	 * @see compressCssFile
+	 * @param array $matches
+	 * @return string the compressed string
+	 */
+	public static function compressCssPregCallback($matches) {
+		if ($matches[1]) {		// Group 1: Double quoted string.
+			return $matches[1];   // Return the string unmodified.
+		} elseif ($matches[2]) {  // Group 2: Single quoted string.
+			return $matches[2];   // Return the string unmodified.
+		} elseif ($matches[3]) {  // Group 3: Regular non-MacIE5-hack comment.
+			return "\n";				// Return single space.
+		} elseif ($matches[4]) {  // Group 4: MacIE5-hack-type-1 comment.
+			return "\n/*\\T1*/\n";  // Return minimal MacIE5-hack-type-1 comment.
+		}
+		elseif ($matches[5]) {  // Group 5,6,7: MacIE5-hack-type-2 comment
+			$matches[6] = preg_replace('/\s++([+>{};,)])/S', '$1', $matches[6]);  // Clean pre-punctuation.
+			$matches[6] = preg_replace('/([+>{}:;,(])\s++/S', '$1', $matches[6]); // Clean post-punctuation.
+			$matches[6] = preg_replace('/;?\}/S', "}\n", $matches[6]);				// Add a touch of formatting.
+			return "\n/*T2\\*/" . $matches[6] . "\n/*T2E*/\n"; // Minify and reassemble composite type2 comment.
+		} elseif (isset($matches[8])) { // Group 8: Non-string, non-comment. Safe to clean whitespace here.
+			$matches[8] = preg_replace('/^\s++/', '', $matches[8]);				   // Strip all leading whitespace.
+			$matches[8] = preg_replace('/\s++$/', '', $matches[8]);				   // Strip all trailing whitespace.
+			$matches[8] = preg_replace('/\s{2,}+/', ' ', $matches[8]);				// Consolidate multiple whitespace.
+			$matches[8] = preg_replace('/\s++([+>{};,)])/S', '$1', $matches[8]);  // Clean pre-punctuation.
+			$matches[8] = preg_replace('/([+>{}:;,(])\s++/S', '$1', $matches[8]); // Clean post-punctuation.
+			$matches[8] = preg_replace('/;?\}/S', "}\n", $matches[8]);				// Add a touch of formatting.
+			return $matches[8];
+		}
+		return $matches[0] . "\n/* ERROR! Unexpected _proccess_css_minify() parameter */\n"; // never get here
+	}
+
+	/**
 	 * Decides whether a CSS file comes from one of the baseDirectories
 	 *
 	 * @param	string	$filename		Filename
@@ -129,7 +256,7 @@
 	protected function checkBaseDirectory($filename, array $baseDirectories) {
 		foreach ($baseDirectories as $baseDirectory) {
 				// check, if $filename starts with $skinStylesheetDirectory (it's position 0, not FALSE!)
-			if (strpos($filename, $baseDirectory) === 0) {
+			if (is_int(strpos($filename, $baseDirectory))) {
 				return TRUE;
 			}
 		}
@@ -141,18 +268,18 @@
 	 *
 	 * @param	string	$contents		Data to process
 	 * @param	string	$oldDir			Directory of the originial file, relative to TYPO3_mainDir
-	 * @param	string	$newDir			Directory of the resulting file
 	 * @return	string	Processed data
 	 */
-	protected function cssFixRelativeUrlPaths($contents, $oldDir, $newDir) {
+	protected function cssFixRelativeUrlPaths($contents, $oldDir) {
 		$matches = array();
-		preg_match_all('/url[\s]*\([\'\"]?(.*)[\'\"]?\)/iU', $contents, $matches);
-		foreach ($matches[1] as $match) {
+
+		preg_match_all('/url(\(\s*["\']?([^"\']+)["\']?\s*\))/iU', $contents, $matches);
+		foreach ($matches[2] as $matchCount => $match) {
 				// remove '," or white-spaces around
 			$match = preg_replace('/[\"\'\s]/', '', $match);
+			$newPath = t3lib_div::resolveBackPath('../../' . TYPO3_mainDir . $oldDir . $match);
 
-			$newPath = t3lib_div::resolveBackPath('../../' . TYPO3_mainDir . $oldDir . $match);
-			$contents = str_replace($match, $newPath, $contents);
+			$contents = str_replace($matches[1][$matchCount], '(\'' . $newPath  . '\')', $contents);
 		}
 		return $contents;
 	}
Index: t3lib/class.t3lib_pagerenderer.php
===================================================================
--- t3lib/class.t3lib_pagerenderer.php	(Revision 7483)
+++ t3lib/class.t3lib_pagerenderer.php	(Arbeitskopie)
@@ -1306,8 +1306,7 @@
 	protected function doConcatenate() {
 		// traverse the arrays, concatenate in one file
 		// then remove concatenated files from array and add the concatenated file
-
-
+		
 		if ($this->concatenateFiles) {
 			$params = array (
 				'jsLibs'         => &$this->jsLibs,
@@ -1365,8 +1364,7 @@
 				}
 			}
 		}
-
-		if ($this->compressCss && $GLOBALS['TYPO3_CONF_VARS'][TYPO3_MODE]['cssCompressHandler']) {
+		if ($this->compressCss) {
 				// use extern compress routine
 			$params = array (
 				'cssInline'  => &$this->cssInline,
@@ -1374,10 +1372,14 @@
 				'headerData' => &$this->headerData,
 				'footerData' => &$this->footerData,
 			);
-			t3lib_div::callUserFunction($GLOBALS['TYPO3_CONF_VARS'][TYPO3_MODE]['cssCompressHandler'], $params, $this);
-		} else {
-			if ($this->compressCss) {
-				// own method, nothing implemented atm
+
+			if ($GLOBALS['TYPO3_CONF_VARS'][TYPO3_MODE]['cssCompressHandler']) {
+				// use extern concatenate routine
+				t3lib_div::callUserFunction($GLOBALS['TYPO3_CONF_VARS'][TYPO3_MODE]['cssCompressHandler'], $params, $this);
+			} elseif (TYPO3_MODE === 'BE') {
+				$compressor = t3lib_div::makeInstance('t3lib_compressor');
+				$cssOptions = array('baseDirectories' => $GLOBALS['TBE_TEMPLATE']->getSkinStylesheetDirectories());
+				$this->cssFiles = $compressor->compressCssFiles($this->cssFiles, $cssOptions);
 			}
 		}
 	}
Index: typo3/template.php
===================================================================
--- typo3/template.php	(Revision 7483)
+++ typo3/template.php	(Arbeitskopie)
@@ -305,6 +305,7 @@
 			);
 			$this->pageRenderer->setLanguage($GLOBALS['LANG']->lang);
 			$this->pageRenderer->enableConcatenateFiles();
+			$this->pageRenderer->enableCompressCss();
 		}
 		return $this->pageRenderer;
 	}