How to define a CSS in Blogger Blog?

We saw How to define a CSS in general HTML?.In blogger,
Places where CSS and HTML used together?

• In posts.
• In HTML/Java Script Gadgets.
• In Overall Template.

In Posts :-

1. The CSS is defined in the HTML part of the post at the top. For example,
   
   <style type="text/css">
   .textborder{border:0.5px solid black;}
   </style>
2. The above code should be pasted at the top of the post. Therefore the post will look like,
   
   <style type="text/css">

   .textborder{border:0.5px solid black;}

   </style>

   <div>
   <div class="textborder">body of the post</div>
   </div>
3. The life span of the style is the life span of the post.

In HTML/ Java Script Gadgets:-

1. Same way as first step, but the you needa place the style in a HTML gadget.
2. HTML/Java Script Gadget? :-
   
   • Dashboard => Design => Page Elements(if necessary) => Add a gadget => HTML/Java Script [Old UI]
   • Dashboard => Layouts => Add a gadget => HTML/Java Script [New UI] 
3. Place the code as below in the gadget.
   
   <style type="text/css">

   .textborder{border:0.5px solid black;}

   </style>

   <div>
   <div class="textborder">body of the HTML Gadget</div>
   </div>
4. The Life span of the style is the life span of the HTML/Java Script Gadget.

In Overall Template:-
   Two ways again :-

1. Go to Add CSS option:-
   
   • Dashboard => Design => Template Designer => Advanced => Add CSS [Old UI]
   • Dashboard => Template => Customize => Advanced => Add CSS[New UI]
   Just Paste the code without <style/> tag. Like below
   
   .textborder{border:0.5px solid black;}
   Click Apply to Blog. 
2. Go to HTML Template Editor. Press Ctrl + F. Find the following code.
   
   ]]></b:skin>
   Paste the CSS that you pasted in previous step just above the found code. Save Template.

How to use the css?

• When you place the CSS in a template, you can use it anywhere inside the Blog. You should just enclose with <div/> tag.
• Like this:-
  
  <div class="textborder">Body of the HTML gadget/Post/Template</div>
• The life span of the style is the life span of the blog.