The Document.visibilityState read-only property returns the visibility of the document, that is in which context this element is now visible. It is useful to know if the document is in the background or an invisible tab, or only loaded for pre-rendering. Possible values are:
The HTML <link> element specifies relationships between the current document and an external resource. Possible uses for this element include defining a relational framework for navigation. This Element is most used to link to style sheets.
document.designMode controls whether the entire document is editable. Valid values are "on" and "off". According to the specification, this property is meant to default to "off". Firefox follows this standard. The earlier versions of Chrome and IE default to "inherit". Starting in Chrome 43, the default is "off" and "inherit" is no longer supported. In IE6-10, the value is capitalized.