fix typo

thanks @cmorten for noticing

Author: scottaohara

index.html

@@ -2791,7 +2791,7 @@ <h2>Definition of Roles</h2>
 				<p>A dialog is a descendant window of the primary window of a web application. For HTML pages, the primary application window is the entire web document.</p>
 				<p>Dialogs are often used to prompt the user to enter or respond to information, or can represent content related to understanding or modifying the content of the primary application window. A dialog that is designed to interrupt workflow and prevent users from interacting with the primary web application is usually modal. See related <rref>alertdialog</rref>. A dialog that allows for the user to switch between interacting with the content of the primary web application and the content the dialog is usually modeless (i.e., non-modal). In lieu of using robust host language features for marking content of the primary web application as <code>inert</code>, authors SHOULD use the <pref>aria-modal</pref> attribute, and constrain focus to dialogs. See the <a href="https://www.w3.org/WAI/ARIA/apg/patterns/dialog-modal/">WAI-ARIA Authoring Practices: Dialog (modal) pattern</a> for additional details on implementing modal dialog design patterns.</p>
 				<p>Authors MUST provide an accessible name for a dialog, which can be done with the <pref>aria-label</pref> or <pref>aria-labelledby</pref> attribute.</p>
-				<p>Authors SHOULD ensure that all dialogs (both modal and non-modal) have at least one focusable descendant element. Authors SHOULD focus an element in the modal dialog when it is displayed, and authors SHOULD constrain keyboard focus to focusable elemenets within a modal dialog, until dismissed.</p>
+				<p>Authors SHOULD ensure that all dialogs (both modal and non-modal) have at least one focusable descendant element. Authors SHOULD focus an element in the modal dialog when it is displayed, and authors SHOULD constrain keyboard focus to focusable elements within a modal dialog, until dismissed.</p>
 				<p>Authors SHOULD provide a dialog an accessible description, with the <pref>aria-describedby</pref> attribute, for instances where authors have set initial keyboard focus on an element that follows content that outlines the purpose of the dialog. Assistive technology SHOULD give precedence to exposing author defined dialog accessible descriptions when a dialog is invoked and user focus is moved to a descendant of the dialog element.</p>
 				<div class="note">
 					<p>Authors are strongly encouraged to use <pref>aria-describedby</pref>, rather than <pref>aria-description</pref>, to provide descriptions to dialogs. While <code>aria-description</code> could be used to provide an accessible description for a dialog, it will provide a better and more consistent user experience to reference visible content that can also be independently read by all users. Doing so will help ensure important descriptive information is less likely to be missed.</p>