The specification for anchor tags has changed in HTML5 to allow <A> tags to contain block-level child elements. For example,
"<a href='#'><h2>HI</h2></a>" would now be valid in HTML5. Here is the new specification:
The problem is that the TinyMCE editor in Orchard will still strip out block-level children in anchor tags with it's current settings.
To reproduce, Create an HTML widget, add in some html markup containing an anchor tag with block-level child element(s) similar to the example I provided. After closing and repoening the HTML edit panel in TinyMCE the HTML markup will have changed, stripping
out the <a> tag.
The fix would be to add this setting to the "orchard-tinymce.js" file in the TinyMCE module: