From http://www.w3schools.com (Copyright Refsnes Data)

SVG Structure

SVG can be defined as a standalone page, as an embedded object, or in an XHTML document with a namespace declaration.

SVG Document Structure

There are three ways of defining SVG in a Web document:

as a standalone SVG page
as an embedded element
in an XHTML document with a namespace declaration

The most powerful method of the three is displaying SVG through the use of namespaces. However, in this section we will only explain the first two methods.

A Standalone SVG Page

The following example defines a standalone SVG file. The file must be saved with an .svg extension:

<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN"
"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">

<svg xmlns="http://www.w3.org/2000/svg"
width="100%" height="100%" x="0" y="0">
  ....
  ....
  ....
</svg>

Since SVG is XML-based most of the search engines will not pick up a standalone SVG page. To solve this problem we can add SVG as an embedded element in an XHTML page.

SVG as an Embedded Element

The following example shows how to embed SVG within an XHTML document:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<body>

<object data="test.svg" width="500"
height="500" type="image/svg+xml">
<embed src="test.svg" width="500"
height="500" type="image/svg+xml" />
</object>

</body>
</html>

The example above is a straightforward XHTML document.

Notice the use of the <object> and <embed> tags. According to the XHTML standard we should only use the <object> tag, but since Netscape does not support this tag we find it best to use both the <object> and <embed> tags.

By using this method the document will be picked up by search engines. This method also makes it easier to integrate other objects (e.g. sound, music, Flash) on the same web page. I think this method is the preferred one, until SVG is supported by the major browsers.