Index: t3lib/class.t3lib_compressor.php
===================================================================
--- t3lib/class.t3lib_compressor.php	(revision 7483)
+++ t3lib/class.t3lib_compressor.php	(working copy)
@@ -105,12 +105,13 @@
 		$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);
+				$compressedFilename = $this->compressCssFile($filename);
+				$contents = file_get_contents(PATH_site . $compressedFilename);
+				$concatenated .= $this->cssFixRelativeUrlPaths($contents, dirname($filename) . '/');
 			}
 
 			if (strlen($concatenated)) {
@@ -121,6 +122,82 @@
 	}
 
 	/**
+	 * Compresses a CSS file
+	 *
+	 * 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)) {
+			$contents = file_get_contents($GLOBALS['BACK_PATH'] . $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.
+
+			t3lib_div::writeFile(PATH_site . $targetFile, $contents);
+		}
+		return $targetFile;
+	}
+
+	public static function compressCssPregCallback($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
@@ -141,10 +218,9 @@
 	 *
 	 * @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) {