Inline Spell-Checker
Previous versions of Opera contained an on-demand spell-checker based on Aspell. Opera 10 introduced an inline spell checker based on Hunspell. This is available in multi-line text areas and in the mail client. As you type, misspelled words are underlined and can be corrected via a right-click menu. The US-English dictionary is included, and there is an interface to download additional dictionaries from within the browser. This inline spell-checker has support for 48 languages.
Read more about this topic: Opera 10, Opera 10.00