[Kai]

That’s not located in a css-file!
You have to edit the PO-file for your language. Use a simple Editor or free PoEdit.
In German, the file is de_DE.po in theme directory.

Look for:

#: inc/structure/header-extensions.php:464
msgid “\”Read More\””
msgstr “\”Mehr…\””

#: inc/structure/header-extensions.php:464
msgid “Read More”
msgstr “Mehr…”

#: inc/structure/header-extensions.php:501
msgid “Page NOT Found”
msgstr “Seite NICHT gefunden”

#: inc/structure/header-extensions.php:503
msgid “Search Results”
msgstr “Suchergebnisse”

#: inc/structure/searchform-extensions.php:19
#: inc/structure/searchform-extensions.php:21
#: inc/structure/searchform-extensions.php:22
msgid “Search”
msgstr “Suche”

and edit the Dutch language.