CSS BASICS

CSS

 Is a style sheet language used for describing the presentation of a document written in a markup language. Most often used to set the visual style of web pages and user interfaces written in HTML and XHTML

Along with HTML and JavaScript, CSS is a cornerstone technology used by most websites to create visually engaging webpages, user interfaces for web applications, and user interfaces for many mobile applications

CSS is used to describe the appearance of the webpage

Oppa, Gangnam Style!

  • Unfortunately, the CSS language is considerably different from the HTML language
  • However, like HTML, it is very easy to understand and write

One ring to rule them all

CSS has a very straightforward syntax. Your CSS is divided into rules. Each rule has two parts: a selector and one or more declarations (each of which has a property and a value). Here's an example rule : 

I choose you!

The selector does exactly what it sounds like: it selects certain parts of your HTML document. There're a few ways for you to do this. The simplest is to simply u se a tag name (this'll select all the <h1> tags in your document):

h1 { 
    *put your declarations here 
}

Keepin' it Classy

Another way is to use IDs and Classes. This is useful if you want to only select one or a few of a certain tag. They both correspond to special attributes that you can use on any tag.

Use IDs to uniquely identify a single tag:

<div id="myfavdiv">Hiyya!</div>

And select them in CSS with a hash (#) followed by the ID:

#myfavdiv { 
    *declarations go here* 
}

Use classes to identify groups of tags:

<div class="smalldivs">itsy-bitsy</div>
<div class="smalldivs">tiny</div>

And select them with a period (.) followed by the class:

.smalldivs { 
    *declarations go here* 
}

Declare war on boring!

Once you've selected a set of elements, use declarations to change their visual properties. Declarations come after a selector, and are enclosed in curly-brackets {like these}. Each declaration has the format:

property: value;

Don't forget that semi-colon! It'll lead to big problems later on!

Fun-sized!

  • Often, you'll want to fine-tune the size of an element. CSS is just the tool for the job!
  • CSS has 4 properties for size 
  • Width and Height do exactly what you'd expect
  • Margin specifies the width of an invisible border OUTSIDE the element's actual border, while
  • Padding specifies the width of an invisible border WITHIN the element's actual border

Background

CSS Units

  • CSS has several different units for expressing a length.
  • Many CSS properties take "length" values, such as width, margin, padding, font-size, border-width, etc.
  • Length is a number followed by a length unit, such as 10px, 2em, etc.
  • A whitespace cannot appear between the number and the unit. However, if the value is 0, the unit can be omitted.
  • For some CSS properties, negative lengths are allowed.
  • There are two types of length units: relative and absolute.

Relative Lengths

em

Relative to the font-size of the element (2em means 2 times the size of the current font)

vw

Relative to font-size of the root element

rem

Relative to 1% of the width of the viewport

vh

Relative to 1% of the height of the viewport

%

Take length in percent

Relative length units specify a length relative to another length property. Relative length units scales better between different rendering mediums.

Absolute Lengths

The absolute length units are fixed and a length expressed in any of these will appear as exactly that size.

cm

centimeters

mm

millimeters

in

inches (1in = 96px = 2.54cm)

points (1pt = 1/72 of 1in)

pt

px

pixels (1px = 1/96th of 1in). Pixels (px) are relative to the viewing device

Units

CSS Colors

Colors are displayed combining RED, GREEN, and BLUE light.

  • CSS colors are defined using a hexadecimal (HEX) notation for the combination of Red, Green, and Blue color values (RGB). The lowest value that can be given to one of the light sources is 0 (HEX 00). The highest value is 255 (HEX FF).
  • HEX values are written as 3 double digit numbers, starting with a # sign.
Color Color HEX Color RGB
  #000000 rgb(0,0,0)
  #FF0000 rgb(255,0,0)
#00FF00 rgb(0,255,0)
  #0000FF rgb(0,0,255)
  #FFFF00 rgb(255,255,0)
  #00FFFF rgb(0,255,255)
  #FF00FF rgb(255,0,255)
  #C0C0C0 rgb(192,192,192)
  #FFFFFF rgb(255,255,255)

Hexadecimal Colors

  • Hexadecimal color values are supported in all major browsers.
  • A hexadecimal color is specified with: #RRGGBB, where the RR (red), GG (green) and BB (blue) hexadecimal integers specify the components of the color. All values must be between 00 and FF.
  • For example, the #0000ff value is rendered as blue, because the blue component is set to its highest value (ff) and the others are set to 00.

RGB Colors

  • RGB color values are supported in all major browsers.
  • An RGB color value is specified with: rgb(red, green, blue). Each parameter (red, green, and blue) defines the intensity of the color and can be an integer between 0 and 255 or a percentage value (from 0% to 100%).
  • For example, the rgb(0,0,255) value is rendered as blue, because the blue parameter is set to its highest value (255) and the others are set to 0.
  • Also, the following values define equal color: rgb(0,0,255) and rgb(0%,0%,100%).

RGBA Colors

  • RGBA color values are supported in IE9+, Firefox 3+, Chrome, Safari, and in Opera 10+.
  • RGBA color values are an extension of RGB color values with an alpha channel - which specifies the opacity of the object.
  • An RGBA color value is specified with: rgba(red, green, blue, alpha). The alpha parameter is a number between 0.0 (fully transparent) and 1.0 (fully opaque).

Selectors

  • CSS selectors allow you to select and manipulate HTML elements.
  • CSS selectors are used to "find" (or select) HTML elements based on their id, class, type, attribute, and more.

Do NOT start a selector name with a number!

element Selector

The element selector selects elements based on the element name.

You can select all <p> elements on a page like this: (all <p> elements will be center-aligned, with a red text color)

id Selector

  • The id selector uses the id attribute of an HTML element to select a specific element.
  • An id should be unique within a page, so the id selector is used if you want to select a single, unique element.

class Selector

The class selector selects elements with a specific class attribute

Grouping Selectors

You can group the selectors, to minimize the code

To group selectors, separate each selector with a comma

Validation

Why Validate?

  • Validation as a debugging tool
  • Validation as a future-proof quality check
  • Validation eases maintenance
  • Validation helps teach good practices
  • Validation is a sign of professionalism

http://jigsaw.w3.org/css-validator/ - Validator

FONT

CSS font properties define the font family, boldness, size, and the style of a text.

Difference Between Serif and Sans-serif Fonts

CSS Font Families

In CSS, there are two types of font family names:

  • generic family - a group of font families with a similar look (like "Serif" or "Monospace")
  • font family - a specific font family (like "Times New Roman" or "Arial")
Generic family Font family Description
Serif Times New Roman
Georgia 		Serif fonts have small lines at the ends on some characters
Sans-serif Arial
Verdana 		"Sans" means without - these fonts do not have the lines at the ends of characters
Monospace Courier New
Lucida Console 		All monospace characters have the same width

Font Family

  • The font family of a text is set with the font-family property.
  • The font-family property should hold several font names as a "fallback" system. If the browser does not support the first font, it tries the next font.
  • Start with the font you want, and end with a generic family, to let the browser pick a similar font in the generic family, if no other fonts are available.
  • Note: If the name of a font family is more than one word, it must be in quotation marks, like: "Times New Roman".

Font Style

The font-style property is mostly used to specify italic text.

This property has three values:

  • normal - The text is shown normally
  • italic - The text is shown in italics
  • oblique - The text is "leaning" (oblique is very similar to italic, but less supported)

Font Size

The font-size property sets the size of the text

  • You should not use font size adjustments to make paragraphs look like headings, or headings look like paragraphs.
  • Always use the proper HTML tags, like <h1> - <h6> for headings and <p> for paragraphs.
  • The font-size value can be an absolute, or relative size.
  • Absolute size:
    • Sets the text to a specified size
    • Does not allow a user to change the text size in all browsers (bad for accessibility reasons)
    • Absolute size is useful when the physical size of the output is known
  • Relative size:
    • Sets the size relative to surrounding elements
    • Allows a user to change the text size in browsers

font variant

In a small-caps font, all lowercase letters are converted to uppercase letters. However, the converted uppercase letters appears in a smaller font size than the original uppercase letters in the text.

normal

The browser displays a normal font. This is default

small-caps

The browser displays a small-caps font

font weight

The font-weight property sets how thick or thin characters in text should be displayed.

normal

Defines normal characters. This is default

bold

normal

lighter

Defines thick characters

Defines thicker characters

Defines lighter characters

100
200
300
400
500
600
700
800
900

Defines from thin to thick characters. 400 is the same as normal, and 700 is the same as bold

CSS Text

CSS gives you precise control over typography in your Web pages, allowing you to set parameters such as the spacing between lines, words and even letters, and the alignment and indenting of text.

Text Color

The color property is used to set the color of the text.

  • a HEX value - like "#ff0000"
  • an RGB value - like "rgb(255,0,0)"
  • a color name - like "red"

With CSS, a color is most often specified by:

Text Alignment

  • The text-align property is used to set the horizontal alignment of a text.
  • Text can be centered, or aligned to the left or right, or justified.
  • When text-align is set to "justify", each line is stretched so that every line has equal width, and the left and right margins are straight (like in magazines and newspapers).

Text Decoration

The text-decoration property is used to set or remove decorations from text

Text Transformation

The text-transform property is used to specify uppercase and lowercase letters in a text.

Text Indentation

The text-indent property is used to specify the indentation of the first line of a text.

direction

The direction property specifies the text direction/writing direction.

ltr

The writing direction is left-to-right. This is default

rtl

The writing direction is right-to-left

letter spacing

The letter-spacing property increases or decreases the space between characters in a text.

line height 

The line-height property specifies the line height.

text-shadow

The text-shadow property adds shadow to text.

text-shadow: h-shadow v-shadow blur-radius color;

h-shadow

v-shadow

blur-radius

color

The position of the horizontal shadow

The position of the vertical shadow

Optional. The blur radius. Default value is 0

Optional. The color of the shadow

vertical align

The vertical-align property sets the vertical alignment of an element.

Value Description
baseline Align the baseline of the element with the baseline of the parent element. This is default
length Raises or lower an element by the specified length. Negative values are allowed
% Raises or lower an element in a percent of the "line-height" property. Negative values are allowed
sub Aligns the element as if it was subscript
super Aligns the element as if it was superscript
top The top of the element is aligned with the top of the tallest element on the line
text-top The top of the element is aligned with the top of the parent element's font
middle The element is placed in the middle of the parent element
bottom The bottom of the element is aligned with the lowest element on the line
text-bottom The bottom of the element is aligned with the bottom of the parent element's font

VERTICAL ALIGN

white space

The white-space property specifies how white-space inside an element is handled.

Value Description
normal Sequences of whitespace will collapse into a single whitespace. Text will wrap when necessary. This is default
nowrap Sequences of whitespace will collapse into a single whitespace. Text will never wrap to the next line. The text continues on the same line until a <br> tag is encountered
pre Whitespace is preserved by the browser. Text will only wrap on line breaks. Acts like the <pre> tag in HTML
pre-line Sequences of whitespace will collapse into a single whitespace. Text will wrap when necessary, and on line breaks
pre-wrap Whitespace is preserved by the browser. Text will wrap when necessary, and on line breaks

WHITE SPACE

word spacing

The word-spacing property increases or decreases the white space between words.

Class work

Create a web page using all the properties from this presentation 

Use inline and and internal styles

Home work

Create a web page using all the properties and all the selectors from this presentation using external stylesheet

THANKS FOR YOUR ATTENTION

CSS Basics

CSS Basics

By Dima Pikulin

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CSS Basics

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