adding html, css and javascript reference material

html_css_resources/code_examples/HTMLCSSCode/Background.css

html_css_resources/code_examples/HTMLCSSCode/Background.html

...resources/code_examples/HTMLCSSCode/BackgroundStretch.css

...esources/code_examples/HTMLCSSCode/BackgroundStretch.html

html_css_resources/code_examples/HTMLCSSCode/BoxModel.css

html_css_resources/code_examples/HTMLCSSCode/BoxModel.html

...esources/code_examples/HTMLCSSCode/DescendantSelector.css

...sources/code_examples/HTMLCSSCode/DescendantSelector.html

..._css_resources/code_examples/HTMLCSSCode/ExternalFile.css

...css_resources/code_examples/HTMLCSSCode/ExternalFile.html

...ss_resources/code_examples/HTMLCSSCode/HTML5Elements.html

...ss_resources/code_examples/HTMLCSSCode/InternalStyle.html

...ss_resources/code_examples/HTMLCSSCode/PseudoElements.css

...s_resources/code_examples/HTMLCSSCode/PseudoElements.html

html_css_resources/code_examples/HTMLCSSCode/Selectors.css

html_css_resources/code_examples/HTMLCSSCode/Selectors.html

...sources/code_examples/HTMLCSSCode/ShorthandProperties.css

...ources/code_examples/HTMLCSSCode/ShorthandProperties.html

...s_resources/code_examples/HTMLCSSCode/TableNoBorders.html

...resources/code_examples/HTMLCSSCode/TableWithBorders.html