Update Navigation Bar Styling and Adding Paragraph Break

[Adrija-G]

Hello,
I've made several enhancements to the navigation bar styling in this pull request:

• Set the position property to fixed to keep the navigation bar at the top.
  

• Adjusted margin-left and width properties for better alignment.
  

• Changed the background-color to #23537a for a new color scheme.
  

• Added padding and margin adjustments for better spacing.
  

• Included a hover effect with a semi-transparent background color.
  

• Changed the color of visited links to light grey.
  

• Made the boxes more visually appealing with additional padding.
  

Additionally, I've added

tags in two other places in the code. The changes have been applied as follows:
Initial Code:
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The Web Security Model

The WG may be called on to advise other WGs or the TAG...

WebCrypto

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Modified Code:
_

The Web Security Model

The WG may be called on to advise other WGs or the TAG...

WebCrypto

_

I have proposed these changes with a view to enhance the document's readability and structure, ensuring that the content is presented in a more organized and user-friendly manner.
Thank you!