GetElement methods not working in Gmail

Question

For some reason, getElementById() and getElementsByClassName() cannot locate many of the elements on gmail. For example, the div entitled "Mail" on the navigation bar has the code:

<div id=":qy" class="z9 z8 T2"><span class="is">Mail</span><div class="Ww4Jzd"></div></div>

Yet running document.getElementById(":qy") in the Chrome console doesn't find it. What am I missing?

Answer 1

They are in iframes. This should do it:

document.getElementById('canvas_frame').contentWindow.document.getElementById(':qy')

Answer 2

IDs may not start with a colon.