Elements should only be used to mark text that has that meaning. This is called the "semantics" of your documents. That's it for elements that are specific to certain types of text. Before we look at any more elements, there are a few basic building blocks of XHTML that we need to cover, so that you can grasp the topics we'll examine next. Hopefully, you now have an understanding of elements, start tags, end tags, the basic structure of an XHTML document, and the text elements we looked at in the previous section.
Character references aren't as intimidating as they sound no need to sweat!
2. Header, Content and Footer
Let's find out why they exist, then we'll look at how to code and use them. Take a look at your keyboard. Unless you're using a pretty strange keyboard, the answer is 'no. How do you know if it's the start of a tag, or an angle bracket used in the content of the document? You don't. Entity references and character references are extremely similar in XHTML, and people often confuse the two names. Basically, both tell the Web browser or User Agent that it should insert a certain character in their place.
If you don't know what the word "character" specifically refers to, it's a catch-all word for a letter, number, punctuation mark, etc. A is one character, AB is two characters, N! P 3 is five characters four? You get the idea. Entity references can represent more than one character in SGML or XML, but that's another story -- you don't need to worry about it right now.
Let's look at the copyright symbol we saw above. To insert a copyright symbol into your document, you'd use either of the following:. If you try the examples above and your Web browser isn't broken you'll see that a copyright symbol displays in both cases. As I said before, the entity reference uses names in this case, " copy " , while the character reference uses numbers here, " ".
First XHTML Example
Observant readers will notice that the character reference also includes a sharp or hash, or pound symbol " ". Let's take a closer look. An entity reference begins with an ampersand, which is followed by the name of the entity reference. The whole is finished with a semi-colon, much in the same way that you use a left angle bracket and right angles bracket to denote delimit the start and end of a tag.
Character references, on the other hand, begin with an ampersand followed by a sharp symbol. This is followed by the number of the character reference, and is finished with a semi-colon. Whether you use an entity reference or a character reference is up to you.
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I tend to use entity references because I find names easier to remember than numbers, but the choice is yours. Just don't forget that you need to include the sharp symbol in the character reference, and not with the entity reference. I'll explain some of the entity and character references available to you in later sections, but I won't show you all of them individually, as there are far too many approximately two hundred and fifty. For your reference, though, I've prepared three articles detailing the three sets available to you:.
Using character or entity references for those characters avoids this problem. The above code is wrong and should be written in one of the two following ways. The first uses entity references, while the second is written with character references:. White space refers to any characters in your document that do not serve any purpose other than creating space.
This includes:. A form feed is the character at the end of each line that tells the computer to start a new line. A zero width space is used to separate words in languages such as Thai. No matter how much space you leave between your words, Web browsers will always reduce it to a single space character. There is one exception to this rule that we'll cover in the next section.
What do I mean when I say "words"? I'm referring to any characters that aren't white space themselves, and which have no white space between them. That might sound a bit complicated, but it's not. An example should help you understand. If you view the above example in a visual browser you'll see that all the content appears on a single line, with a single space between each word.
That's all there is to it. This feature comes in very handy! It means you can use tabs, spaces and new lines to make your code easier to read, and not worry about your document looking funny in a visual browser. You need to be careful about putting white space around your tags, until you get used to this rule. Then it will become second nature. If you want a space to appear before or after a word that's contained by an element, you should put that space outside the element.
By this I mean you should insert space before the start tag, and after the end tag. If you put the space inside the tags, you might not get any white space between your words. On some Web browsers there may not be any space displayed between the words "not" and "inside". When you create your documents, you may want to include information in the code for yourself or others who view the document code. But how can you ensure this information doesn't appear to users who view the document in a Web browser?
You'll need to use what we call a "comment". A comment has the following syntax:. You should be careful not to use two dashes together within your comments, as this could be interpreted by the browser to mark the end of the comment even without the right angle bracket. As you'll see if you view this example, the text in the comments is ignored. Comments are useful for leaving yourself reminders, such as notes on what still needs to be completed in a document. We've seen how to use special characters in our pages with character references and entity references, we've looked at the way white space is handled, and we've also seen how you can add comments to your code.
In the next section, we'll continue our coverage of the elements you can use that relate to text, including headings, line breaks and pre-formatted text.
X_ITE X3D Browser
In this section we'll look at more of the elements and a couple of entity references in the XHTML arsenal that relate to text, further to those covered in the section "Text That Says Something". Before we start, I'd like to re-iterate an important point: all elements should be used for their meanings, and not the visual effects they generate. You can make any element look exactly the way you want using style sheets we'll be covering this topic in some detail later on.
There are many benefits to this approach, the most important being that it makes your site much more accessible to disabled users, and those who use alternative browsers such as Personal Digital Assistants and in-car browsers.
Valid XHTML 1.0 - Frameset example
It also helps you attain a suitable search engine placement. Any document that's longer than a few sentences needs to be split up into sections if it's to be usable. This concept was not invented specially for the Web -- it was probably conceived soon after writing was invented.
As the number associated with the element increases, so does the level of depth of the subheading to which that element is applied. The six elements are:. It's important that you use the heading elements to mark your headings, as this ensures visitors using all kinds of user agents can understand your document structure.
It also helps you achieve higher rankings in search engines, as the search engines can gain a better idea of what your document is about by examining the headings. Here's a sample three-level document.
1. Template Layout
I'm sure you can work out from this, what a document with deeper levels would look like. View example 1. Subse-quent examples include comments in the markup, especially to highlight new features. Some important elements of an XHTML doc-ument are the html element, the head element and the body element. The html element encloses the head section represented by the head element and the body section repre-sented by the body element. The head section also can contain special document formatting instructions called style sheets and client-side programs called scripts for creating dynamic web pages.
Presentational markup describes the appearance of the text, regardless of its function. Most presentational markup elements have become deprecated under the HTML 4. Hypertext markup links parts of the document to other documents. Let's now look at attributes. Attributes are written within the start tag of an element, after the element's name.
The abbreviation element, abbr , can be used to demonstrate these various attributes:. In most browsers, pointing the cursor at the abbreviation should display the title text "Hypertext Markup Language. Empty elements consist of only a single tag, with any attributes. Attributes define desired behavior or indicate additional element properties. In keeping with the principle of Separation of Concerns , the function of HTML is primarily to add structural and semantic information to the raw text of a document.
In other words: HTML just defines what kind of text or typographic elements you have inside a document , e.
Web browsers have a built-in method to render each of these elements, e. The advantage of this strategy is that you may use the same style for lots of pages, e. This also means, that you can easly change the look of all your page that use the same styelsheet s.
Finally, you may associate several stylesheets to a page and that offers an extra set functionalities. For example, you can load a large "official" stylesheet that will cover most of your needs and then you can fine-tune styling by adding your own on top. You also may create different stylesheets for different media, in particular: one for normal viewers, one for visually impaired viewers and one for printing that filters out elements like navigation menus that you won't need on pager.
Markup of an HTML page is divided into two big parts: the head contains information that the user will not see inside the browser window and the body contains the contents to be displayed. We can express this with a simple formula:. You may have a look at the real page by clicking here. However, this HTML code is not totally complete. There exist different variants for HTML. Let's now look at a larger gallery of complete examples before we start introducing X HTML elements and attributes.
HTML 4. Correct HTML files should include the following document type declaration information starting on line 1. Before we add more explanation we suggest that you either use HTML 4. The rationale for including this information is that display will be better when the browser knows what kind of X HTML you intended to use. As a web designer you must cope with several issues. Here are some of these issues that you should look at once you'll get past learning basic HTML:. In the head element we may defines various important information about an HTML page.
Its contents are not displayed. Specifies links to other documents, such as previous and next links, or alternate versions. A common use is to link to external stylesheets, using the form:. Can be used to specify additional metadata about a document, such as its author, publication date, expiration date, page description, keywords, or other information not provided through the other header elements and attributes.
For instance, the content attribute defines both the mime type and the character set. Define a document title. User agents e. Typically, the title is displayed on the window decoration. For obvious reasons, only text is allowed within a title element. It then goes on for dozens of lines. Many modern web pages though use reasonably short headers.
Inside the body tag, a variety of high level elements may used in any order. The following pseudo-formal rule includes the most important ones:. Read the rule like this: Inside the body tag you may include any of these tags as much as you like and in any order.