Default Styles lesson: Add missing word (#27792)

* Fix missing word

* Remove unnecessary apostrophe

Co-authored-by: MaoShizhong <122839503+MaoShizhong@users.noreply.github.com>

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Co-authored-by: MaoShizhong <122839503+MaoShizhong@users.noreply.github.com>

intermediate_html_css/intermediate_css_concepts/default_styles.md

@@ -11,11 +11,11 @@ This section contains a general overview of topics that you will learn in this l
 
 ### What are default styles and where do they come from?
 
-As you have worked on projects, you likely observed default styles applied to certain elements, such as larger and bolder headings on `h1` elements, and blue, underlined links on `a' elements. There is also a good chance you struggled with things like default margins and padding. These styles are part of the user-agent stylesheets, ensuring basic styling for webpages without CSS. Each browser has it's own set of user-agent stylesheets so the default styles do slightly between browsers.
+As you have worked on projects, you likely observed default styles applied to certain elements, such as larger and bolder headings on `h1` elements, and blue, underlined links on `a' elements. There is also a good chance you struggled with things like default margins and padding. These styles are part of the user-agent stylesheets, ensuring basic styling for webpages without CSS. Each browser has its own set of user-agent stylesheets so the default styles do vary slightly between browsers.
 
 ### What if I don't like the defaults?
 
-With very few exceptions you can simply write your own CSS rules.  The rules you write in your stylesheet have higher precedence than the user-agents rules, and therefore overwrite the defaults. However, there is another option.
+With very few exceptions you can simply write your own CSS rules. The rules you write in your stylesheet have higher precedence than the user-agents rules, and therefore overwrite the defaults. However, there is another option.
 
 To address inconsistencies across browsers and establish a consistent starting point for styling, some developers started using CSS resets. These resets are stylesheets containing CSS rules aimed at altering or removing the defaults set by user-agent stylesheets. Using them can help achieve consistency, and can provide a clean slate for developers to apply their styles without interference.