Simply put: It's not feasible to achieve that using HTML or CSS.
HTML serves as a markup language rather than a programming one, dictating how browsers display your webpage. Similarly, CSS determines the styling of elements based on classes or ids, lacking the capability for conditional logic like traditional programming languages.
What are your options?
You can turn to javascript. This versatile scripting language allows you to identify the current page and dynamically modify text content or alter classes to apply specific CSS rules. Implementing this feature in javascript is relatively straightforward with numerous resources available online, including libraries like jQuery for simplifying tasks.
To retrieve the current page through javascript, refer to this solution:
Get current URL in web browser
Alternatively, consider employing server-side languages like PHP. By adjusting headers based on requested pages, you can achieve the desired outcome. However, this method may be excessive if only header changes are necessary.