How has firefox/gecko HTML+CSS rendering changed in version 38? -

i have a little website header no longer renders correctly, since updating firefox 38.0.5 [the faceplant logo missing top right, , main logo no longer centred]. still renders expected in other browsers. how has engine's rendering changed in update?

according mdn, list of changes is:

css

• support ruby-position , ruby-align have been added , available default (bug 1055676, bug 1123917 , bug 1039006).
• the :unresolved pseudo-class has been implemented custom elements (bug 1111633).
• the predefined style ethiopic-numeric uses space, instead of dot, suffix match recent change spec (bug 1120721).
• css transitions on generated content (with ::before , ::after) on both inline , block splits them start expected specification (bug 1110277).
• the implementation of css logical properties made big progress. [...]
• how css transitions start has been modified match recent change of specifications, aiming @ having interoperable behavior between browsers (bug 960465).

html

• the <label> element no longer dispatches events label target element if interactive content found between event target , label (bug 229925).
• the <picture> element has been activated default (bug 1017875).