This used to be my method many years ago, when both the Internet and my relationship with it was still very young. Meanwhile things have evolved. Now, when I write a typo, the spell checker warns me by showing a little squiggly red line underneath the misspelled word.
This feature can be found in Firefox browser and it is strongly connected to the Language dictionaries that are installed on your browser. For example, in my case, I have installed dictionaries for Romanian and English. Every time I mistake a word in the selected language, the spell checker corrects me. It's really easy and convenient. Just one right-click on the red line and I get several suggestions.
But the spell checker isn't perfect. Sometimes, it "underlines" a correct word. How can you add that word to the dictionary? Sounds complicated but it isn't. The last versions of Firefox allows users to customise the dictionary (and thus the spell checker).
I use as example a couple of old screenshots from my own browser. In the image bellow, I edit a question on AskUbuntu and, as you can see, the spell checker marks as typos several words including "paranoical".
But this word is not a typo, it it is correct. So, in order to add this word to the dictionary I right click on the underlined word and then click on "Add to Dictionary".
|To add a word to the dictionary right-click on it and then click on Add to Dictionary|
And then, the line disappears - the word is now kept in the personal dictionary. This way, everyone can enrich and complete the dictionary making it more trustworthy and useful.
|The added word is no longer underlined.|