Classes get stripped out: why? I am pasting the following code into the text editor.

&lt;ul class="faqs"&gt;    
&lt;li class="navbookmark"&gt;&lt;a href="#er1"&gt;ABC&lt;/a&gt;&lt;/li&gt;
&lt;/ul&gt;


After the initial save everything looks fine in preview mode. However, if I go back in to edit the page, the styles applied to ul and li tags get stripped out, and the source looks like this.

&lt;ul&gt;
    &lt;li&gt;&lt;a href="#er1"&gt;ABC&lt;/a&gt;&lt;/li&gt; 
&lt;/ul&gt;


How do I prevent this from happening?
I haven't met this problem before. I did Google search and found this link Classes being stripped in CKeditor. Maybe your problems come from CKeditor and you just configure the allowedContent for CKeditor.