Update ReadMe

Author: mhasanmeet

README.md

@@ -27,9 +27,51 @@
 ###  CSS : Cascading Style Sheets
 
 <details>
-  <summary>H</summary>
+  <summary>The Important Cascade Algorithm</summary>
 
-* V
+* CSS Execution Order
+* CSS Combinators
+* CSS Inheritance
+	
+</details>
+
+<details>
+  <summary>Important Topics</summary>
+
+* CSS Selectors
+* CSS position
+* Flexbox
+* Z-index (content position)
+* Margin, Padding
+* Overflow
+* CSS Shadows
+* CSS function
+	
+</details>
+
+<details>
+  <summary>Topics for Efficient CSS coding</summary>
+
+* CSS Shorthands
+* CSS Pseudo Code (Class & Elements)
+* CSS custom coding: CSS root
+* CSS Custom Coding: CSS variable
+* CSS Breakpoints
+* Sizing units
+	
+</details>
+
+<details>
+  <summary>More to cover</summary>
+
+* CSS Preprocessor
+    * SCSS
+	* LESS
+* CSS Framework
+	* Bootstrap
+	* Tailwind
+* CSS Normalize
+* CSS in JS
 
 </details>