Translate the strings as required and remove any untranslated strings from the file.
For example, given the following exported strings:
33872|HTML\
33873|Tab delimited text file\
33874|Export\
33875|Format:\
33876|Only Active applet\
33877|All applets in view\
33878|Output file name\
33879|Browse...\
33880|And paste output to clipboard\
33881|And open file\
Translate the required strings and remove any untranslated strings as follows:
33873|Archivo delimitado por tabulaciones\
33874|Exportar\
33875|Formato:\
33876|Sólo el applet activo\
33877|Todos los applets de la vista\
33878|Nombre del &archivo de salida:\
33880|Y pegar salida en el &portapapeles\
33881|Y &abrir el archive
NOTE: Strings 33872 and 33879 were removed from the userstr.txt, because they were not required to be translated.