diff --git a/blocks/online_users/block_online_users.php b/blocks/online_users/block_online_users.php
index 75540933cb5..a24a1ea75c5 100644
--- a/blocks/online_users/block_online_users.php
+++ b/blocks/online_users/block_online_users.php
@@ -112,7 +112,7 @@ class CourseBlock_online_users extends MoodleBlock {
         //Calculate minutes
         $minutes  = floor($timetoshowusers/60);
 
-        $this->content->text = "<font size=\"-2\"><div align=\"center\">(".get_string("periodnminutes","block_online_users",$minutes).")</div></font>";
+        $this->content->text = "<center><font size=\"-2\">(".get_string("periodnminutes","block_online_users",$minutes).")</font></center>";
 
         //Now, we have in users, the list of users to show
         //Because they are online
@@ -145,7 +145,7 @@ class CourseBlock_online_users extends MoodleBlock {
             ob_end_clean();
 */
         } else {
-            $this->content->text .= "<font size=\"-1\"><p align=\"center\">".get_string("none")."</p></font>";
+            $this->content->text .= "<center><font size=\"-1\">".get_string("none")."</font></center>";
         }
 
         return $this->content;
diff --git a/course/lib.php b/course/lib.php
index faf19a642b6..38e5ba86565 100644
--- a/course/lib.php
+++ b/course/lib.php
@@ -960,6 +960,8 @@ function print_section($course, $section, $mods, $modnamesused, $absolute=false,
                 echo "</tr>";
             }
         }
+    } else {
+        echo "<tr><td></td></tr>"; // needed for XHTML compatibility
     }
     if ($ismoving) {
         echo '<tr><td><a title="'.$strmovefull.'"'.
@@ -1141,7 +1143,7 @@ function print_category_info($category, $depth) {
         $catimage = "&nbsp";
     }
 
-    echo "\n\n".'<table border="0" cellpadding="3" cellspacing="0" width="100%"><tr>';
+    echo "\n\n".'<table border="0" cellpadding="3" cellspacing="0" width="100%">';
 
     if ($CFG->frontpage == FRONTPAGECOURSELIST) {
         $courses = get_courses($category->id);
@@ -1333,24 +1335,24 @@ function print_course_search($value="", $return=false, $format="plain") {
     $strsearchcourses= get_string("searchcourses");
 
     if ($format == 'plain') {
-        $output  = '<center><p align="center" class="coursesearchbox">';
-        $output .= '<form name="coursesearch" action="'.$CFG->wwwroot.'/course/search.php" method="get">';
-        $output .= '<input type="text" size="30" name="search" value="'.$value.'" />';
+        $output  = '<form name="coursesearch" action="'.$CFG->wwwroot.'/course/search.php" method="get">';
+        $output .= '<center><p align="center" class="coursesearchbox">';
+        $output .= '<input type="text" size="30" name="search" alt="'.$strsearchcourses.'" value="'.$value.'" />';
         $output .= '<input type="submit" value="'.$strsearchcourses.'" />';
-        $output .= '</form></p></center>';
+        $output .= '</p></center></form>';
     } else if ($format == 'short') {
-        $output  = '<center><p align="center" class="coursesearchbox">';
-        $output .= '<form name="coursesearch" action="'.$CFG->wwwroot.'/course/search.php" method="get">';
-        $output .= '<input type="text" size="12" name="search" value="'.$value.'" />';
+        $output  = '<form name="coursesearch" action="'.$CFG->wwwroot.'/course/search.php" method="get">';
+        $output .= '<center><p align="center" class="coursesearchbox">';
+        $output .= '<input type="text" size="12" name="search" alt="'.$strsearchcourses.'" value="'.$value.'" />';
         $output .= '<input type="submit" value="'.$strsearchcourses.'" />';
-        $output .= '</form></p></center>';
+        $output .= '</p></center></form>';
     } else if ($format == 'navbar') {
-        $output = '<table border="0" cellpadding="0" cellspacing="0"><tr><td nowrap="nowrap">';
-        $output .= '<form name="coursesearch" action="'.$CFG->wwwroot.'/course/search.php" method="get">';
-        $output .= '<input type="text" size="20" name="search" value="'.$value.'" />';
+        $output  = '<form name="coursesearch" action="'.$CFG->wwwroot.'/course/search.php" method="get">';
+        $output .= '<table border="0" cellpadding="0" cellspacing="0"><tr><td nowrap="nowrap">';
+        $output .= '<input type="text" size="20" name="search" alt="'.$strsearchcourses.'" value="'.$value.'" />';
         $output .= '<input type="submit" value="'.$strsearchcourses.'" />';
-        $output .= '</form>';
         $output .= '</td></tr></table>';
+        $output .= '</form>';
     }
 
     if ($return) {
@@ -1760,4 +1762,4 @@ function make_editing_buttons($mod, $absolute=false, $moveselect=true, $indent=-
            " alt=\"$str->delete\" /></a>$hideshow$groupmode";
 }
 
-?>
\ No newline at end of file
+?>
diff --git a/lib/weblib.php b/lib/weblib.php
index 2fb908523d8..e7ef7d4a315 100644
--- a/lib/weblib.php
+++ b/lib/weblib.php
@@ -1506,8 +1506,8 @@ function print_footer ($course=NULL, $usercourse=NULL) {
 /// Course links
     if ($course) {
         if ($course == 'home') {   // special case for site home page - please do not remove
-            $homelink  = '<p align="center"><a title="moodle '. $CFG->release .' ('. $CFG->version .')" href="http://moodle.org/" target="_blank">';
-            $homelink .= '<br /><img width="100" height="30" src="pix/moodlelogo.gif" border="0" /></a></p>';
+            $homelink  = '<a title="moodle '. $CFG->release .' ('. $CFG->version .')" href="http://moodle.org/" target="_blank">';
+            $homelink .= '<br /><img width="100" height="30" src="pix/moodlelogo.gif" border="0" alt="moodlelogo" /></a>';
             $course = get_site();
             $homepage = true;
         } else {
@@ -2950,9 +2950,9 @@ function obfuscate_text($plaintext) {
         $c = ord($plaintext{$i});
         $numerical = ($c >= ord('0')) && ($c <= ord('9'));
         if ($prev_obfuscated and $numerical ) {
-            $obfuscated.='&#'.ord($plaintext{$i});
+            $obfuscated.='&#'.ord($plaintext{$i}).';';
         } else if (rand(0,2)) {
-            $obfuscated.='&#'.ord($plaintext{$i});
+            $obfuscated.='&#'.ord($plaintext{$i}).';';
             $prev_obfuscated = true;
         } else {
             $obfuscated.=$plaintext{$i};