html - How to detect if JavaScript is disabled?

I've figured out another approach using css and javascript itself.
This is just to start tinkering with classes and ids.

The CSS snippet:
1. Create a css ID rule, and name it #jsDis.
2. Use the "content" property to generate a text after the BODY element. (You can style this as you wish).
3 Create a 2nd css ID rule and name it #jsEn, and stylize it. (for the sake of simplicity, I gave to my #jsEn rule a different background color.

The JavaScript snippet:
1. Create a function.
2. Grab the BODY ID with getElementById and assign it to a variable.
3. Using the JS function 'setAttribute', change the value of the ID attribute of the BODY element.

The HTML part.
1. Name the BODY element attribute with the ID of #jsDis.
2. Add the onLoad event with the function name. (jsOn()).

Because of the BODY tag has been given the ID of #jsDis:
- If Javascript is enable, it will change by himself the attribute of the BODY tag.
- If Javascript is disable, it will show the css 'content:' rule text.

You can play around with a #wrapper container, or with any DIV that use JS.

Hope this helps to get the idea.