upgading from v1.5.18 to ???? - Joomla! Forum - community, help and support

hi everybody.....new in joomla, yes......i'm little bit confused upgrading. i'm redecorating old site , website version 1.5.18. have information in joomla control panel joomla! security newsfeed upgrade 2.5.5. version. possible or not? version recomended site?
please

1. upgrade 1.5.26 witch latest version of 1.5 series. use 1.5.0-1.5.26 patch package.

2. 2.5.5 non working version. don't use it. latest 2.5.6, 1.5->2.5 migration.
http://docs.joomla.org/migrating_from_joomla_1.5_to_joomla_2.5

the template , extension must 2.5 compatible in order migrate.