try the Desktop Bookmarklet Rated 4 out of 5 stars

I tried upping the max version to 10 in the .rdf file but it still would not work for me.

Then found that a YSlow bookmarklet is available: http://developer.yahoo.com/yslow/mobile/#javascript:%28function%28y,p,o%29{p=y.body.appendChild%28y.createElement%28%27iframe%27%29%29;p.id=%27YSLOW-bookmarklet%27;p.style.cssText=%27display:none%27;o=p.contentWindow.document;o.open%28%29.write%28%27%3Chead%3E%3Cbody%20onload=%22YUI_config={win:window.parent,doc:window.parent.document};var%20d=document;d.getElementsByTagName%28\%27head\%27%29[0].appendChild%28d.createElement%28\%27script\%27%29%29.src=\%27http://d.yimg.com/jc/yslow-bookmarklet.js\%27%22%3E%27%29;o.close%28%29}%28document%29%29

This review is for a previous version of the add-on (3.0.4.1-signed).