Describe the critical rendering path of the browser: from entering the URL in the address bar to rendering the page. Talk about DNS, TCP, HTTP, DOM construction, CSSOM, Render Tree, Layout, and Paint.

When a user enters a URL and presses Enter, the browser begins the page loading process, which includes several key stages:

1. DNS Lookup — the browser contacts the DNS server to convert the domain name into an IP address.

2. Establishing TCP connection — a connection is established with the server using the TCP protocol with the obtained IP.

3. HTTP request — the browser sends an HTTP request to the server to retrieve the HTML document.

4. Receiving the response and starting HTML parsing — the server returns HTML, and the browser begins constructing the DOM (Document Object Model) — a tree of page elements.

5. Loading and parsing CSS — CSS files are loaded in parallel, and based on them, the CSSOM (CSS Object Model) is built.

6. Building the Render Tree — the browser combines the DOM and CSSOM to create a rendering tree containing only visible elements with their styles.

7. Layout (Reflow) — the exact sizes and positions of elements on the page are calculated.

8. Paint — the browser paints pixels on the screen, displaying the content.

This process repeats during dynamic page changes. Optimizing each stage is important for fast content loading and rendering.