Added css for correct displaing (#24307)

guide/english/certifications/responsive-web-design/basic-css/size-your-images/index.md

@@ -6,7 +6,7 @@ title: Size Your Images
 For sizing your images, first create your class in your style tag.
 
 An example:
-```
+```css
 <style>
   .fixed-image {
     width: 500px;
@@ -15,6 +15,6 @@ An example:
   ```
   
   You can then add the class to your image:
-  ```
+  ```css
   <img class="fixed-image" src="http://www.example.com/picture"/>
   ```