Merge pull request web#18 from charle44/patch-5

grammatical change

04 CSS3.md

@@ -536,7 +536,7 @@ body {
 
 The next task is to build a navigation menu bar to the website using CSS. Depending on the number of menu items, the menu bar can contain multi-level menus.
 
-A menu bar is be defined as an HTML unordered list. Each menu in a menu bar is a list item.
+A menu bar can be defined as a HTML unordered list. Each menu in a menu bar is a list item.
 
 The menus can contain submenus. A submenu is coded as a list that is within the parent menu's list item.