Hi vespanut, the error you show there will occur if you try to edit HTML code using TextEdit.app .

What happens is when you put in HTML attributes like value="something" , unfortunately TextEdit replaces the simple double quote characters with different "Open quote" and "Close quote" characters (they kind of swish in different directions for the open vs closed ones) and then that is not valid HTML anymore.

You'll need to instead use a text editor that does not do any kind of "word processing" like character replacement in order to make properly formed HTML code. A couple of choices for that are the Atom text editor (which is free) or Sublime text which is paid but pretty popular.

Or also I just tried looking if there was some way to disable that quote changing in TextEdit and it looks like that may be possible under Edit > Substitutions and uncheck Smart Quotes, but I haven't had a chance to test that myself.

- Michael

Also one other thing for editing HTML files in TextEdit.app - to edit the HTML source code you need to set Preferences > Open and Save tab > "Display HTML files as HTML code instead of formatted text". Otherwise when you open it instead of editing the actual code it will try to show the rendered HTML as if it was a rich text document.

- Michael