Courses/Design & Technique-Essential Web Design/04

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selectors

Example http://codepen.io/anon/pen/YGpPyy

CSS selectors allow the selection of html elements to be styled.
Their scope can be very broad, such as all the elements (*), or all the elements that that share a given tag.
To more fine grained selectors, like descendents and id.
To pseudo class selectors, that are triggered by a certain action.


element

p {font-weight:bold}

All(star)

*. Star targets all the elements in a page p {font-weight:bold}

id

#. Id targets the (only 1) element with the given id p#foo {font-weight:bold}.

class

.. Class targets several elements that share the same class .bar {color: blue}


id vs class

Class-id.png

descendents

elements that are descendents another element, like the anchors within a list item, and not other anchors li a{color:gree;}.

direct descendents

elements that direct children of another element li > a{color:gree;}.

pseudo classes

E.g.

  • All links that have been visited a:visited {transform: rotate(0.5turn)};
  • when hoverving a link a:hover{background: red;}

More on Pseudo Classes: https://developer.mozilla.org/en/docs/Web/CSS/Pseudo-classes

More on CSS selectors in

Positioning

CSS position property determines where an element will be positioned.

Example: http://codepen.io/anon/pen/VKKWgY

position:static

  • the default position
  • dont offset possibilities
  • are positioned according to their default behavior

position: relative

  • very similar to that of the static value
  • position is in relation to the containing / parent element
  • Main difference: relative value accepts box offset properties top, right, bottom left.
  • Box offset properties allow precise positioning


position: absolute

  • elements accept box offset properties (left,right, top, bottom)
  • elements are removed from the normal flow of the document
  • and positioned in relation to the body element
  • off-set property are set in relation to the body and not containing element. E.g. top: 10px; will place the element 10px offset from the top of the browser window.

Interesting art work using absolute position and Google books image: http://www.julienlevesque.net/books-scapes/

position: fixed

  • similar to absolute: off-set set in relation to the body
  • but the positioning is relative to the browser viewport
  • not scrolling with the page.
  • always present, as if fixed to the screen

Based on http://learn.shayhowe.com/advanced-html-css/detailed-css-positioning/


More on position

Display

Example: http://codepen.io/anon/pen/mAAwLJ

Every element on a web page is a rectangular box.

The CSS display property determines how that box is displayed next to its sibling elements - how do they organize themselves


Possible values for display

  • inline OR inline-block: elements are displayed in a line.
    • inline-block: display the element in a line, like inline, but allows more formatting possibilities: width, height, margin to the right and left of the box

displayInline.png

  • block: Each element is standalone, occupying the entire width of its parent box and line breaks before and after it. displayBlock.png
  • none: Turns off the display of the element


More on display property on:

centering elements

http://www.w3.org/Style/Examples/007/center.en.html