How do I change the grey line separating articles?
How do I change the layout of an article?
The layout of each article is controlled by a form. Go to textpattern > presentation > forms and edit the one used by your page template (probably ‘default’, unless you’ve changed it).
Alternatively, you can create a new article form and use that to display articles. For more information, see ‘How do I select which form is used to display articles?’