In jira-application.properties, there is an option:
jira.search.fullcontentview.pagebreaks=true
which causes CSS to be emitted in the Full Content view to break pages at issue boundaries. This keeps IE users happy (see JRA-4226), but makes Firefox users unhappy (se JRA-8085). We should:
a) Investigate what the issue with Firefox is, and if necessary raise a bug with Mozilla
b) Make the option settable in General Configuration, if there is no other option.