Best Way to View Generated Source of Webpage?

Question

I'm looking for a tool that will give me the proper generated source including DOM changes made by AJAX requests for input into W3's validator. I've tried the following methods:

1. Web Developer Toolbar - Generates invalid source according to the doc-type (e.g. it removes the self closing portion of tags). Loses the doctype portion of the page.
2. Firebug - Fixes potential flaws in the source (e.g. unclosed tags). Also loses doctype portion of tags and injects the console which itself is invalid HTML.
3. IE Developer Toolbar - Generates invalid source according to the doc-type (e.g. it makes all tags uppercase, against XHTML spec).
4. Highlight + View Selection Source - Frequently difficult to get the entire page, also excludes doc-type.

Is there any program or add-on out there that will give me the exact current version of the source, without fixing or changing it in some way? So far, Firebug seems the best, but I worry it may fix some of my mistakes.

Solution

It turns out there is no exact solution to what I wanted as Justin explained. The best solution seems to be to validate the source inside of Firebug's console, even though it will contain some errors caused by Firebug. I'd also like to thank Forgotten Semicolon for explaining why "View Generated Source" doesn't match the actual source. If I could mark 2 best answers, I would.

Answer 1

Justin is dead on. The key point here is that HTML is just a language for describing a document. Once the browser reads it, it's gone. Open tags, close tags, and formatting are all taken care of by the parser and then go away. Any tool that shows you HTML is generating it based on the contents of the document, so it will always be valid.

I had to explain this to another web developer once, and it took a little while for him to accept it.

You can try it for yourself in any JavaScript console:

el = document.createElement('div');
el.innerHTML = "<p>Some text<P>More text";
el.innerHTML; // <p>Some text</p><p>More text</p>

The un-closed tags and uppercase tag names are gone, because that HTML was parsed and discarded after the second line.

The right way to modify the document from JavaScript is with document methods (createElement, appendChild, setAttribute, etc.) and you'll observe that there's no reference to tags or HTML syntax in any of those functions. If you're using document.write, innerHTML, or other HTML-speaking calls to modify your pages, the only way to validate it is to catch what you're putting into them and validate that HTML separately.

That said, the simplest way to get at the HTML representation of the document is this:

document.documentElement.innerHTML