Adding 404 Not found Page

[Harsha19-08]

Issue Description

If the url is not valid we will be directed to 404 not found page

Steps to Reproduce

trying to find unknown page through the website it will appear with just a simple 404 not found page

Expected Behavior

It will be suitable if the links not leading to any other pages

Additional context

Assign me this issue under so that i can work on that