There are couple of modules which are used for language translation like locale and i18n

i have installed both. For french, i used the po file from here http://drupal.org/project/fr

but still there are blocks which are not translated...

though french translation doc says 97% have been translated ...

Comments

If you have additional modules installed that do not belong to the Drupal Core Installation, then it's likely that those are not translated. Some of them have either a translation available when you install them or provide at least the template to translate it on your own – but unfortunately not every one.

In such a case, you might ask the modules authors for a template file, translate it and then provide the translation to the community.

Way to go!

That's how it should be done!

Michael