https://www.w3schools.com/Html/
Just search what you are trying to do i.e post image html and use this site. Got the suggestion here years ago.
The problem isn’t knowing html. I have about 30,000 pages of html on the web. The problem is knowing why Free Republic is MUNGING the html. The sandbox is giving normal html commands. The problem is that FR isn’t accepting them. Haven’t found a sentence yet that says that they trash tables, but somewhere that seems to be what is happening.