On the staff client, when visiting a biblio on detail.pl or an auth on a Authority search results authorities-home.pl (on some other places too) we can see a very plain MARC preview. Inside #marcPreview there is a table with a very basic formatting and no class to let the user (or Koha devs on staff-global.scss) improve the view through CSS. Would be useful a set of classes on each section of the MARC (biblio and auth) records. For example: leader-tag leader-value field-control-tag field-control-value field-data-tag field-data-value indicators ind1 ind2 subfield-char subfield-code subfield-value. subfield-char would be particularly useful to change easier the yazy _ to a traditional $ or ‡. For biblios would be also neat for e.g.: leader-00-04 leader-05 leader-06 leader-07 leader-08 leader-09 leader-10 leader-11 leader-12-16 leader-17 leader-18 leader-19 leader-20 leader-21 leader-22 field-008-07-10 field-008-11-14 field-008-15-17 field-008-18-34 field-008-35-37 field-008-38 field-008-39.