diff --git a/markdown.php b/markdown.php
index d296dfd..fb4527f 100644
--- a/markdown.php
+++ b/markdown.php
@@ -2554,7 +2554,7 @@ class MarkdownExtra_Parser extends Markdown_Parser {
 				)
 				
 				# 2: CSS classes
-				\s?(\.[^\n]+)?
+				[ ]*(\.[^\n]+)?
 				
 				[ ]* \n # Whitespace and newline following marker.
 				
@@ -2570,7 +2570,7 @@ class MarkdownExtra_Parser extends Markdown_Parser {
 				\1
 				
 				# 4: CSS classes
-				\s?(\.[^\n]+)?
+				[ ]*(\.[^\n]+)?
 				
 				# End of line
 				[ ]* \n
@@ -2582,6 +2582,12 @@ class MarkdownExtra_Parser extends Markdown_Parser {
 	function _doFencedCodeBlocks_callback($matches) {
 		$codeblock = $matches[3];
 		$codeblock = htmlspecialchars($codeblock, ENT_NOQUOTES);
+		/*
+		Newlines must be replaced with <br />'s because otherwise extra tabs and spaces will
+		be shown depending on where the Markdown'ed content appears in the HTML source. This
+		ensures that code blocks are only a single line in the HTML source and no extra
+		spaces can appear.
+		*/
 		$codeblock = preg_replace_callback('/\n+/',
 			array(&$this, '_doFencedCodeBlocks_newlines'), $codeblock);
 		$class     = ! empty($matches[2]) ? $matches[2] : ( ! empty($matches[4]) ? $matches[4] : '');