updated lesson 4 in coach document

Author: Helen Brockelbank

coaches/lesson-guide.md

@@ -85,8 +85,22 @@ of a tutorial the student should be focussing on.
 
 ### Prerequisites
 
+- A web browser
+- A text editor
+- Able to read and write html syntax
+- Able to read and write a simple CSS rule
+
 ### Learning goals
 
+- Some understanding of how to use HTML to structure content in a document
+- Understand floats
+- Some understanding of the following position values:
+  - `static`
+  - `relative`
+  - `absolute`
+  - `fixed`
+- Some understanding of z-index
+
 ## Lesson 5: Diving into HTML5 and CSS3
 
 ### Prerequisites