Offset: Fix comment typo, thanks @AurelioDeRosa

src/offset.js

@@ -117,7 +117,7 @@ jQuery.fn.extend({
 			elem = this[ 0 ],
 			parentOffset = { top: 0, left: 0 };
 
-		// Fixed elements are offset from window (parentOffset = {top:0, left: 0}, because it is it's only offset parent
+		// Fixed elements are offset from window (parentOffset = {top:0, left: 0}, because it is its only offset parent
 		if ( jQuery.css( elem, "position" ) === "fixed" ) {
 			// We assume that getBoundingClientRect is available when computed position is fixed
 			offset = elem.getBoundingClientRect();