Datasheet

XML — eXtensible Markup Language. This is a generic, text- and tag-based language used to describe data

and is used as the base language for many other languages, including XHTML.

So, XHTML is in fact largely just HTML rewritten with XML rules. These rules are pretty simple, and

most of the time VWD will help you get it right or show you a list of errors and suggestions on how to

fix them.

Always Close Your Elements

In XHTML, all elements must be closed. So when you start a paragraph with , you must use some-

where later in your page to close the paragraph. This is also the case for tags that don’t have their own clos-

ing tags, like

<img> or (to enter a line break). In XHTML, these tags are written as self-closing tags,

where the closing slash is embedded directly in the tag itself as in

<img src=”Logo.gif” /> or .

Always Use Lower Case for Your Tag and Attribute Names

XML is case sensitive, and XHTML applies that rule by forcing you to write all your tags in lowercase.

Although the tags and attributes must be in all lowercase, the actual value doesn’t have to be. So, the

previous example that displays the logo image is perfectly valid XHTML, despite the uppercase L in

the image name.

Always Enclose Attribute Values in Quotes

Whenever you write an attribute in a tag, make sure you wrap its value in quotes. For example, when

writing out the

<img> tag and the src attribute, write it like this:

and not like this:

Note that you could also use single quotes to enclose the attribute value, as in this example:

It’s also sometimes necessary to nest single and double quotes. When some special ASP.NET syntax

requires the use of double quotes, you should use single quotes to wrap the attribute’s value:

<asp:Label ID=”DescriptionLabel” runat=”server” Text=’<%# Eval(“Description”) %>’ />

You’ll see this syntax used a lot more in other chapters in this book.

For consistency, this book uses double quotes where possible in all HTML that ends up in the client.

Nest Your Tags Correctly

When you write nested tags, make sure that you first close the inner tag you opened last, and then close

the outer tag. Consider this correct example that formats a piece of text with both bold and italic fonts:

This is some formatted text

Chapter 1: Getting Started with ASP.NET 3.5

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