I\'m working on a site right now where I need to build a URL before putting the button on the page. Here\'s how it works:
var googleplus = $(\"
Here is the solution, it works for me in both IE7/8:
var gPlusOne = document.createElement('g:plusone');
gPlusOne.setAttribute("size", "tall");
gPlusOne.setAttribute("href", "http://google.com");
container.appendChild(gPlusOne);
it appears that using innerHTML to insert a <g:plusone></g:plusone>
element into a page does not work in IE7/8, Create the g:plusone element directly like this: document.createElement('g:plusone').
see more: http://www.google.com/support/forum/p/Webmasters/thread?tid=3d63228b915dab32