Markdown is forgiving enough that a document can look “mostly right” while still containing structural mistakes. A live preview is useful because it lets you review the rendered document rather than reading punctuation in the source.
Check the heading hierarchy
Use one clear top-level heading for the document when appropriate, then move through sections in a logical order. Jumping from an H2 to an H4 may look fine visually in some themes, but it makes the document harder to navigate and less meaningful to assistive technology.
Read every link as a reader would
A label such as “click here” loses context when links are scanned separately. Prefer descriptive link text. Also look for accidentally included spaces, missing parentheses and relative links that only work in your local folder.
Inspect code blocks, especially indentation
Triple-backtick fences are easier to maintain than large indented blocks for many technical documents. Add a language identifier when your publishing system uses it for syntax highlighting. Confirm that backticks inside the example do not accidentally close the block.
Lists reveal spacing mistakes quickly
If a numbered list unexpectedly restarts or a bullet becomes plain text, the source probably has inconsistent indentation or blank lines. Nested lists deserve a quick visual check because different Markdown implementations can vary slightly.
Предпросмотр tables on narrow screens
Markdown tables can become extremely wide. A table with ten columns may be technically valid and still be miserable on mobile. If the information reads better as a list or several smaller tables, choose readability over showing everything in one grid.
Do not rely on Markdown for sanitization
Some Markdown renderers allow embedded HTML and some strip it. Treat untrusted input carefully. A preview tells you how text renders; it does not by itself prove that the final publishing pipeline is secure.
Finish with a plain reading pass
After fixing syntax, stop looking at the Markdown and read the preview from top to bottom. Does the opening explain what the page is for? Can someone find the main steps quickly? Does the ending tell them what to do next? Good formatting supports the content; it does not replace it.