Cross-Origin Resource Sharing, or CORS, defines a way to enable client-side cross-origin requests. So, if this API is used on
http://siteA.org then a resource on http://siteB.org could opt in to this( e.g. by specifying Access-Control-Allow-Origin: as a response header). http://siteA.org
The problem it aims to solve is that AJAX calls that use XMLHttpRequest to do cross-domain requests (e.g. Site A wants to access a script on Site B) are forbidden by web browsers (see Same-origin policy:
Note: WebSockets are not subject to the same-origin policy.
CORS is a W3 Recommendation released on 16th January 2014. See
Alternatives to CORS are:
document.domain property Cross-document messaging – e.g. calling the
postMessage() method on a Window object
Browser support for CORS:
>= Firefox 3.5
>= Safari 4
>= Chrome 3
>= IE10 (IE8+ has partial support). i.e. IE9 in Compatibility View would not support CORS
>= Opera 12
The visual formatting model is how user agents (usually browsers) process the document tree (e.g. HTML) for visual media (e.g. your computer screen).
Each element (e.g. an H1 or div) generates boxes (see the earlier post on the “box model”).
The layout depends on:
box size and type (e.g. div or span)
positioning scheme (e.g. normal flow, float, absolute positioning)
relationship between elements in the document tree
external information (e.g. viewport (e.g. window), image size)
The model does NOT specify all aspects of formatting. E.g. it doesn’t specify a letter-spacing algorithm.
The position of an element’s box are calculated relative to a rectangle called the containing block. This can be the window or viewing area on screen (called the “viewport”).
1.2 Containing blocks
Box positions and sizes are calculated using the edges of a rectangular box called a containing block (usually the viewport) and is anchored at the canvas origin.
See other posts for more on the Visual formatting model. E.g.
Controlling box generation;
Relationships between ‘display’, ‘position’, and ‘float’;
Comparison of normal flow, floats and absolute positioning;
Plenty more here:
Not quite as awesome as an automatic post categoriser but still pretty handy:
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