I've found this to be a good indentation strategy for ERB:

```
<ul>
  <% @bookmarks.each do |bookmark| %>
    <li>
      ...
    </li>
  <% end %>
</ul>
```

That is, indent one level for the contents of HTML elements, and also indent one level anywhere you would normally indent in Ruby. This makes it easier to spot when either of the two languages has been invalidly nested.