http://msdn.microsoft.com/en-us/library/ms533897(VS.85).aspx
Remarks
The innerHTML property is valid for both block and inline elements. By definition, elements that do not have both an opening and closing tag cannot have an innerHTML property.
The innerHTML property takes a string that specifies a valid combination of text and elements. When the innerHTML property is set, the given string completely replaces the existing content of the object. If the string contains HTML tags, the string is parsed and formatted as it is placed into the document.
This property is accessible at run time as the document is being parsed; however, removing elements at run time, before the document is fully loaded, could prevent other areas of the document from rendering.
When using innerHTML to insert script, you must include the defer attribute in the script element.
The innerHTML property is read-only on the col, colGroup, frameSet, html, head, style, table, tBody, tFoot, tHead, title, and tr objects.
You can change the value of the title element using the document.title property.
To change the contents of the table, tFoot, tHead, and tr elements, use the table object model described in Building Tables Dynamically. However, to change the content of a particular cell, you can use innerHTML.
Security Warning: Improper handling of the innerHTML property can enable script-injection attacks. When accepting text from an untrusted source (such as the query string of a URL), use createTextNode to convert the HTML to text, and append the element to the document using appendChild. Refer to the Examples section below for more information.
To maintain compatibility with earlier versions of Windows Internet Explorer, this property applies to the textArea object. However, the property works only with strings that do not contain tags. With a string that contains a tag, this property returns an error. It is better to use the innerText property with this object.
Examples
The following example demonstrates how to convert the HTML source to text using a temporary div element and createTextNode. Once the HTML is sanitized, it can be safely inserted into the document using innerHTML.