@elizabrock  When we use @user = User.find_by(username: params[:username]), the code fails in like this: 
NoMethodError in Users#show
Showing /Users/millerkatiej/nss-squawker/app/views/users/show.html.haml where line #3 raised:

undefined method `gravatar_url' for nil:NilClass

That is why we switched to parameterize rather than friendly_id. Any suggestions?