Have you ever needed to post an important message to all editors about an article, on the article itself, but thought it would stick out like a sore thumb and ruin the article if you did? Are you reverting many edits on an article because editors just aren't seeing the important message or special instructions on the talk page?
The solution is that you can insert hidden text in the article! That way, only the people editing the page will see your message! Here is how to insert a hidden comment:
First, begin the comment by typing <!--
Once you have done that, type what you need the editors to read
Then, end the comment by typing -->
Once you have completed those 3 easy steps, you won't be reverting as many mistakes!
For example, the following hidden comment has been used in the Meaning of life article, in the Popular views section:
<!--Please do not add 42 in this section. It is covered under the section titled "Popular culture treatments". Thank you.-->
Some more examples of pages that have hidden messages include:
The "perfect" Wikipedia article is built on solid research (remember to cite your sources). Contrary to popular belief, not all information is available for free on the Internet. Some research is only published in scientific journals and books (ask your library for remote lending services); some material is available only in commercial, password-protected electronic databases. If you have access to useful research material, please add the relevant information to Wikipedia:WikiProject Resource Exchange, a central portal to find Wikipedians with access to such resources. Remember we can only use facts from sources such as these, not a particular copyrighted expression thereof.
If you are a qualified user you can request access to the databases of paywalled resources proctored by The Wikipedia Library. Qualification usually involves having 500–1000 main namespace edits and 6–12 months tenure editing on Wikipedia.