Not possible, at least not directly. Some thoughts:

1. Use Drupal multilingual tools to store multiple-language-versions of node content including titles.
2. Use Page Title module to generate custom tags from CCK fields, tokens, etc.
3. Use a custom field using an input filter that allows HTML to store this "title", theme your content type to display this field instead of the default title field.

Node title is plaintext only and will likely remain that way.

It is not possible, at least not directly. Some thoughts:

1. Use Drupal multilingual tools to store multiple-language-versions of node content including titles.
2. Use the Page Title module to generate custom <title> tags from CCK fields, tokens, etc.
3. Use a custom field using an input filter that allows HTML to store this "title", theme your content type to display this field instead of the default title field.

Node title is plain text only and will likely remain that way.