There are several formatting rules commonly used on the internet, particularly in online written communication. Here are a few of the most common:

1. Bold (strong text): This is used to emphasize important or significant words or phrases.

2. Italics (_italics_): Italics are often used to indicate foreign words, book titles, website names, or to add emphasis to specific words.

3. Underlining (_underlined text_): Underlining is sometimes used to create hyperlinks, but this practice has become less common with the widespread adoption of clickable links.

4. Strikethrough (~strikethrough~): Strikethrough text is typically used to indicate that something is no longer relevant or has been removed.

5. Headings: Various heading tags (

,

, etc.) are used to create hierarchical headings and subheadings in online text.

6. Lists: Lists can be created using bullet points (*) or numbered lists (1., 2., etc.) to present items in a structured format.

7. Hyperlinks: Hyperlinks (also known as links) are clickable text or images that, when clicked, take the reader to another document or website.

8. Blockquotes (>): Blockquotes are used to set off quoted material, typically indented with a greater-than sign (>) at the beginning of each line.

9. Emojis: Emojis, which are small digital images or icons, are often used to convey emotions or ideas in informal online communication.

10. Hashtags (#): Hashtags are used in social media and online discussions to categorize posts or content and make them easier to find.

These formatting rules help improve the readability, structure, and visual appeal of online content. However, specific formatting guidelines may vary depending on the platform or context in which you're communicating. It's important to adapt these rules based on the style and conventions used in your particular online environment.