The spellcheck attribute uses values of true or false (you cannot simply add the spellcheck attribute to a given element):

<!-- spellcheck everything! -->
<input type="text" spellcheck="true" /><br />
<textarea spellcheck="true"></textarea>
<div contenteditable="true" spellcheck="true">I am some content</div>

<!-- spellcheck nothing! -->
<input type="text" spellcheck="false" /><br />
<textarea spellcheck="false"></textarea>
<div contenteditable="true" spellcheck="false">I am some content</div>

You can use spellcheck on INPUT, TEXTAREA, and contenteditable elements.  Thespellcheck attribute works well paired with the autocomplete, autocapitalize, and autocorrect attributes too!

Added from David Walsh's article on Spell Check.