“It is a damn poor mind that can think of only one way to spell a word.” - Andrew Jackson
We're not going to judge. We've all got those few words that we need help with. Because Celtx is a browser-based software, you can use your browser's spellcheck option for all those sneaky little e's before i's and the like. Since Celtx is browser based, you can also use the browser's built-in spell checker. You'll be able to adjust your dictionary regionally and add unrecognized words to your dictionary.
In the Celtx Online Studio editor, the spell checker can be invoked by choosing "edit, check spelling" in the editor itself. The shortcut key is specific to the browser and operating system in use.
Once loaded, the spell checker will start off after your cursor and detect any potential spelling errors and offer the option to "Change", "Change All", "Ignore", or "Add to Dictionary". There are also a number of different languages to choose from:
Once finished you can dismiss the spell checker by choosing "Edit, check spelling" (1, then 2) or by clicking the "X" in the upper right corner of the checker, itself (3):