USING THE SPELLCHECK ATTRIBUTE
Run 
<!Doctype html>
<html>
    <head>
        <title>
            HTML5 Spell check attribute
        </title>
    </head>
    <body>
        <form>
            <textarea style="width:300px;height:150px;border:1 em solid black" spellcheck="false"
                contenteditable="true">spell check off</textarea><br/>
                <textarea style="width:300px;height:150px;border:1 em solid black" spellcheck="true"
                contenteditable="true">spell check on</textarea><br/>
                
        </form>
    </body>
</html>