diff --git a/includes/common.inc b/includes/common.inc
index 27fa190..ab730ed 100644
--- a/includes/common.inc
+++ b/includes/common.inc
@@ -3713,6 +3713,20 @@
       "$1",
       $contents
     );
+
+    // Extract all content declarations for replacement after whitespace cleanup.
+    $css_content_pattern = "/content:\s*($double_quot|$single_quot)/";
+    preg_match_all($css_content_pattern, $contents, $css_content_matches);
+
+    // Replace all content declarations with placeholder comments.
+    if ($css_content_matches) {
+	    $contents = preg_replace_callback($css_content_pattern, function($matches){
+	    	static $count = 0;
+	    	$count++;
+	    	return !empty($matches[1]) ? '/*content:' . $count . '*/' : '';
+	    }, $contents);
+    }
+
     // Remove certain whitespace.
     // There are different conditions for removing leading and trailing
     // whitespace.
@@ -3734,6 +3748,13 @@
       '$1$2$3',
       $contents
     );
+
+    // Replace all content placeholder comments with original declarations.
+    if ($css_content_matches) {
+	    preg_match_all("/\/\*content:\d\*\//", $contents, $css_content_comment_matches);
+	    $contents = str_replace($css_content_comment_matches[0], $css_content_matches[0], $contents);
+    }
+
     // End the file with a new line.
     $contents = trim($contents);
     $contents .= "\n";