I know this goes without saying in most cases, but please, PLEASE validate your HTML when developing with Rails (or any framework really)!

Nasty typos in HTML can have very adverse effects on embedded Ruby code. Recently, I had a <TABLE> I did not close properly in one document. Then, much later in the page, embedded in 2 layers of partials, some ajax fancy-pants-ness. Specifically, I was doing something like

<%= form_remote_tag :url => {:action => "save_note", 
                             :id => note.id}, 
                             :update => "row" + note.id.to_s %>
  <%= text_field "save_note", "note_text" %>
<%= end_form_tag %>

Well my little HTML snafu was causing some Ajax calls to work perfectly, but in this case, I was getting some very quirky results. They were accessing the proper action in the controller, but were not passing any of the form data into @params!

Now of course if I had simply reached up and clicked Validation->Validate HTML on my handy-dandy Web Developer Toolbar I could have saved myself a lot of grief. Lesson learned!