An attribute defines certain values for an element. For example, in <a
href="#">top</a>, the href attribute defines where the link jumps to.
Some attributes have default values, so you can leave them out. For example, <form> has an
attribute method with a default of "get", so you don't have to write method="get" out
in full. Some attributes have no default values and will have to be present. In the case of
<form>, the action attribute must always be there.
CSS
Short for Cascading Style Sheets. This is the name of the language that stylesheets
are written in.
deprecated
When a feature is deprecated, that means it is no longer recommended. There are other features better suited
for the job, and support for the feature may be phased out in future browsers.
DOCTYPE declaration
The declaration of the Document Type; what kind of document it is and how you
would like it displayed. (Not how you want it to be parsed though, in contrast to popular belief.)
This is a piece of markup declaration on top of the HTML or XHTML document.
DOCTYPE definition (DTD)
The definition of what the contents of the document look like. Used in classic HTML and XHTML (but not in
HTML5), usually in the form of a file stored on the W3C website.
element
The basic unit a HTML file is divided into. Most elements consist of a start tag, content and an end tag.
The content can contain other HTML elements. Some elements consist of only a start tag; those are called void
elements.
entity
A character, or a run of characters, that has a name with which you can refer to it. E.G. the
< character has lt for an entity name, so you can refer to it with
<.
HTML has many built in entity names; some dialects contain different ones than others. And some kinds of HTML let
you define your own entities; in XHTML you can put [<!ENTITY smiley ":)">] just
before the > of the DOCTYPE and then write &smiley; in the text for a smiley
&smiley;
Frameset DOCTYPE
A DOCTYPE meant for containing frames - windows onto other documents, rather than having content.
Now defunct.
HTML
HyperText Markup Language. Traditionally, an application of SGML, but starting with
HTML5, a stand-alone language.
MIME type
The standard. cross-operating-system, way of assigning types to files.
For example, the MIME type of a HTML file is "text/html".
The acronym MIME stands for Multipurpose Internet Mail Extensions, but don't let that distract you, it's not just for mail!
obsolete
When a feature is obsolete, that means you should no longer use it. There are other features better suited to
do the same job, and browsers are not required to support it.
optional
When a feature is optional, it does not have to be present in the source. For instance, li
elements have optional end tags in HTML: it's not necessary to write </li>.
One difference between HTML and XHTML is that XHTML doesn't have a concept of optional tags. It does however,
have optional elements: in HTML the start and end tags for the tbody element are optional;
in XHTML, the tbody element itself is optional. Same for colgroup.
property
A (style) property is one of the many styles an element can have.
Quirks mode
A special display mode that browsers use to display old HTML documents the way they were supposed to be
displayed back when they were written.
Most browsers don't do a very good job of this though, for instance Firefox's Quirks mode is a far cry from what
Netscape 4 looked like.
selector
In a stylesheet, that which you assign the style to. For instance, article {color:green} assigns
the value green for the property color to the selector article.
SGML
Standardized General Markup Language. A very versatile language that HTML and XML
are applications of.
Standards mode
The display mode used to render ordinary HTML and XHTML documents.
Contrast with Quirks mode, the display mode used for older (20th century) HTML pages.
Strict DOCTYPE
A Document Type that triggers standards mode in browsers. Actually most DOCTYPE declarations trigger standards
mode, but there are a handful officially defined ones that are recommended, and that are used by the W3C
validator to check if the pages conforms to the rules.
style
When talking about an element, a style is the collection of properties of the element.
tag
Delimiter for a HTML element.
The tag at the start is called the start tag; the one at the end is the end tag.
For example, in <a href="#">top</a>, the <a href="#"> is the start
tag and the </a> is the end tag.
Transitional DOCTYPE
A DOCTYPE allowing the use of 20th century elements like font and center while still
passing the W3C Validator. Not recommended: for new webpages, use a DOCTYPE declaration that triggers Standards
mode, and to emulate 20th century webpages, you shouldn't include a DOCTYPE at all. Doing so will trigger Quirks
mode (which is specifically meant to cater to those old webpages); the Transitional one triggers Almost Standards
Mode, a mode which is almost, but not quite, entirely unlike Quirks.
UTF
Short for Unicode Transformation Format. This is a way of encoding all the 100,000+
Unicode characters. The most prevalent encoding form is the 8-bit one, UTF-8 (which is upward compatible with
ASCII), but you also have 7-bit, 16-bit and 32-bit encoding forms.
W3C
The World Wide Web Consortium develops open standards, protocols and guidelines for
the web.
W3C Validator
An online service that checks if a given webpage conforms to the standard. http://validator.w3.org. There are validators for HTML, CSS, RSS, etc.
XML
eXtensible Markup Language. Originally an SGML application, but slowly leaving its
SGML roots behind.
XML declaration
A processing instruction for the version of the XML eXtensible Markup Language and the encoding. Not needed if
the version is 1.0 and the encoding is UTF-8.
XML prologue
Everything before the start tag of the root element. May consist of processing instructions like an XML
declaration, stylesheet includes and such, markup declarations like the DOCTYPE declaration, comments
etc.
XHTML
eXtensible HyperText Markup Language, a reformulation of HTML in XML.