added day four readme to repo

Author: gixxerblade

weekTwo/dayFour/dayFour.md

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+# Intro Into CSS
+
+CSS, or cascading style sheets, is a language used to describe reusable styles for presenting documents written in a markup language.
+ Its concept was originated by Håkon Wium Lie in 1994.
+  In December 1996, CSS was made a specification by the W3C and today allows web developers to alter the layout and appearance of their web pages.
+   For example, CSS may be used to change the font used in certain HTML element, as well as its size and color.
+    A single CSS file may be linked to multiple pages, which allows a developer to change the appearance of all the pages at the same time.
+
+`Selector` : Define the elements to which a set of CSS rules apply.
+`property` : Human-readable identifiers that indicate which stylistic features you want to change.
+`value` : Indicates how you want to change stylistic features.
+
+## Border Box Model
+
+![Box Model](https://github.com/Vets-Who-Code/Curriculum/blob/master/images/boxmodel.png)
+
+CSS Basic Box Model is a module of CSS that defines the rectangular boxes—including their padding and margin—that are generated for elements and laid out according to the visual formatting model.
+
+`content area`: Bounded by the content edge, contains the "real" content of the element, such as text, an image, or a video player. Its dimensions are the content width (or content-box width) and the content height (or content-box height). It often has a background color or background image
+
+`padding area`: Bounded by the padding edge, extends the content area to include the element's padding.
+
+`border area`: Bounded by the border edge, extends the padding area to include the element's borders.
+
+`margin area`: Bounded by the margin edge, extends the border area to include an empty area used to separate the element from its neighbors.