Fall 2006 week 2: 09/20

1. TOPICS: You will be quizzed over this week's and last week's material next week.
   1. LINK   XHTML;
   2. LINK   CSS;
   3. LINK   Empty Tags;
   4. LINK   Images;
2. HOMEWORK: LINK   Download this week's homework here:
3. QUESTIONS: Here are some questions to help guide you through this weeks' material:
   • What does the abbreviation XHTML stand for?
   • What is XML?
   • What is the difference between XHTML and conventional HTML?
   • What are some of the standards that should guide the typing of strict XHTML?
   • What does CSS stand for? What is it used for?
   • What is the difference between XHTML and CSS?
   • What is an empty tag? What are some examples of empty tags?
   • What attribute must be used with the <img/> in order to place an image into a web page?
4. INTRODUCE: 
   1. XHTML: is an abbreviation for eXtensible HyperText Markup Language, and is not a separate language from HTML. Instead, it is a variation, much like the difference between the language that you use to write an essay for your English class and street slang. The primary differences is that it has stricter standards than conventional HTML. It is actually an attempt to marry the standards for XML (eXtensible Markup Language) to the purpose of HTML, creating web pages.     XML is a cross-platform markup language, used primarily for organizing the information in databases. However, since some devices (such as wireless devices) cannot run web-browsers to display the data and information of databases stored on servers, conventional web-pages (created with HTML) may not be displayed on them. HTML is the markup language used specifically for web browsers on ordinary laptop and desktop computers, not for smaller handheld devices.     XML has very rigid standards of construction and organization. Therefore, as a way to merge the two mark-up languages, and as a way to prepare for the day when all browsing will be done with XML (so as to make all web-pages cross-platform), stricter standards were created for HTML. Thus the formation of XHTML.     As the standards had been, HTML standards are actually quite loose and forgiving. It is possible to make many mistakes and even leave out some tags when typing HTML and still have the web-browser translate the code and present it correctly. This is unreliable, however, as the composer of the code never knows what might come out as a result of the mistakes. Fortunately, web-browsers can decode both HTML and XHTML equally as if there were no difference between them. XHTML, comparatively, has much more rigid standards, and those are the standards that we will use for the creation of our web-pages in this class:
      1. All tags and their attributes must be typed in lower case;
      2. Quotation marks must surround the values for all attributes;
      3. Units must be supplied for all attribute values where necessary;
      4. All tags must be closed and typed in pairs—except in the case of open tags such as <img/> and <br/>
      5. All empty tags must be typed in the XHTML format with the closing slash before the second angle bracket;
      6. Some conventional HTML inline tags are deprecated. This means that these tags are not considered a legitimate part of the language and are not to be used if strict standards are being followed. The primary reason for this is that CSS is preferred and can perform all of the same functions more efficiently and with greater flexibility
      7. A doctype (DTD) indicator must be present at the start of the document. For this reason, if you make mistakes when typing XHTML, the browser will likely not register them, and your page will still be rendered properly. Nonetheless, you would still not be typing XHTML (just standard HTML), and your code would not be able to undergo any scrutiny by an XHTML code validator (see: http://validator.w3.org).
   2. CSS: otherwise known as Cascading Style Sheets, is not a programming language, and neither is it a mark-up language (as is HTML). It is a series of formatting indications made to a web-browser. When the browser reads these specifications, it carries them out on a particular web-page or set of web-pages. For this reason, the tags—primarily some of the in-line tags—that have mostly to do with formatting, are considered deprecated. This means that they will eventually be eliminated and no then longer considered part of the code. Some of these deprecated tags are <b>, <i>, <u>, and <font>.     CSS is a much more efficient way to accomplish the tasks that these tags once did, as most of the styling is centralized in a couple of locations, either in the head of a document or in a separate document altogether devoted solely to CSS, instead of being dispersed throughout the various bodies of documents. Moreover, much more styling and formatting can be accomplished with CSS than standard HTML was ever capable of.   code tasks:     XHTML—organization and structure of data in a web page.     CSS—presentation and aesthetics of the data in a web page.
   3. Empty Tags: Last week there were two types of tags mentioned, block tags, and inline tags. To review, the task of block tags is to organize information into categories. There are seven categories, six levels for headings tags and then for ordinary paragraph text. These seven categories serve to set off text into distinct blocks according to how important it is.     Inline tags make up the other set of HTML tag. As noted, they serve primarily for presentation rather than organization, and therefore are concerned about the look of the text. So, whereas the block tags create blocks, the in-line tags distinguish text within these blocks with various colors, typefaces, sizes and other factors that modify appearance.     There is a third set of tags, however, known as empty tags. These tags are called empty because they do not format content. All other tags surround text or other content: one tag goes in front of the content (or text) and the second tag goes at the end, where one marks the beginning and the other marks the end. Empty tags do not operate in this way. They do not surround content because they do not come in pairs. They are singular tags and as a result are considered empty. Furthermore, they do not surround content but rather generate it, or create it. One empty tag creates a vertical blank space in a web-page, another draws a horizontal line, while yet another creates an image.
      1. The<br/> tag is one example of an empty tag, and it also known as the break tag . It creates a specific kind of content. It does not create text characters, but rather it creates a blank character, also known as a breaking space. It is called a breaking space because it breaks the line and starts anything that follows back at the margin on the next line. Many of these tags may be used together to create multiple breaking spaces, or to push content further down.
      2. The<hr/> tag is another example of an empty tag, otherwise known as the hard rule tag . It creates a specific kind of content, not text nor spaces, but a horizontal line across the page. This tag may be modified by three attributes:
         1. size which alters the thickness of the line;
         2. width which sets the distance of the line extending across the web-page; and
         3. color which, obviously, changes the color of the line. Like the bgcolor attribute for the <body> tag, and the color attribute for the <font> tag, the color is set using the Hexadecimal Color Code.
      3. The<img/> tag is the third example of an empty tag (there are still others), otherwise known as the image tag. It creates a specific kind of content, not text, spaces, or lines, but an image. However, alone this tag does nothing other than indicate to the browser where the image should go (before some bit of text and after some other bit of text, for example). It does not tell the browser which image to put there. In order to do that, an attribute must be used that indicates which image file from your set of folders is to be drawn into the web-page. This attribute is the src attribute, or source attribute. For the value of this attribute, you must type three (3) things:
         1. the location of the file (usually the images folder within the main folder;
         2. the name of the file (typed without spaces); and, followed by
         3. the 3 or 4-letter file extension .