xhtml compliance

lang/en/help/assignment/mods.html

@@ -1,4 +1,4 @@
-<p><img valign="middle" src="<?php echo $CFG->wwwroot?>/mod/assignment/icon.gif">&nbsp;<b>Assignments</b></p>
+<p><img alt valign="middle" src="<?php echo $CFG->wwwroot?>/mod/assignment/icon.gif">&nbsp;<b>Assignments</b></p>
 <ul>
 <p>Assignments allow the teacher to specify a task that requires students 
    to prepare digital content (any format) and submit it by uploading it 

lang/en/help/chat/chatting.html

@@ -5,7 +5,7 @@
 <dl>
 <dt><b>Smilies</b></dt>
 <dd>Any smiley faces (emoticons) that you can type elsewhere in Moodle 
-    can also be typed in here and they will be displayed correctly.  For example,  :-) = <img src="pix/s/smiley.gif">  </dd>
+    can also be typed in here and they will be displayed correctly.  For example,  :-) = <img alt src="pix/s/smiley.gif">  </dd>
  
 <dt><b>Links</b></dt>
 <dd>Internet addresses will be turned into links automatically.</dd>

lang/en/help/choice/mods.html

@@ -1,4 +1,4 @@
-<p><img valign="middle" SRC="<?php echo $CFG->wwwroot?>/mod/choice/icon.gif">&nbsp;<b>Choices</b></p>
+<p><img alt valign="absmiddle" src="<?php echo $CFG->wwwroot?>/mod/choice/icon.gif">&nbsp;<b>Choices</b></p>
 <ul>
 <p>A choice activity is very simple - the teacher asks a question and specifies a 
    choice of multiple responses.  It can be useful as a quick poll to 

lang/en/help/dialogue/info.html

@@ -30,5 +30,6 @@
     students in their own group (assuming the dialogue allows student-to-student
     dialogues). In this mode students who are not in any group do not see any 
     other students.</li>
+</ul>
 </p>