2nd days: What is namespace _ basic tutorial

Day 1: After the namespace DOCTYPE is declared, the following code is:

Generally, our HTML4.0 code isWhat is "xmlns" here?

This "xmlns" is short for XHTML namespace and is called the "namespace" declaration. What is the role of namespace? Alibaba Cloud understands that:

Because xml allows you to define your own identifiers, the identifiers you define may be the same as those defined by others, but they indicate different meanings. Errors may occur when files are exchanged or shared. To avoid such errors, XML uses namespace declarations, allowing you to identify your identity through a URL. For example:

Both Mr. Wang and Mr. Li define Identifier, if John's namespace is "http://www.xiaowang.com", Lee's namespace is "http://www.xiaoli.com", then when two documents exchange data, it will not be confused Because it belongs to different namespaces.

The more common explanation is that namespace is to mark the document and tell others who the document belongs. But this "who" is replaced by a URL.

XHTML is the identifier language for the transition from HTML to XML. It must comply with XML document rules, so you also need to define the namespace. Because XHTML1.0 cannot customize the identity, so its namespace is the same, is "http://www.w3.org/1999/xhtml ". It doesn't matter if you don't quite understand it. At present, we only need to copy the code.

The following lang = "gb2312" specifies that your document is in simplified Chinese.