What situations can cause the parsing process of an HTML document to be suspended or blocked?

Parsing of an HTML document can be paused or blocked in the following situations:

• When encountering a <script> tag without the async or defer attribute — the browser stops parsing, loads, and executes the script so that the script can influence subsequent HTML.
• When loading external resources that affect rendering — for example, CSS files that block rendering until they are loaded.
• If a script modifies the DOM or uses document.write — this requires stopping parsing to correctly apply changes.

In Node.js, if an HTML parser is used, blocking can occur while waiting for asynchronous operations, such as loading external resources or executing scripts, if the parser supports such logic.

Thus, the main reason for blocking is to ensure the correct order of script execution and resource loading so that the page displays correctly.