Try disabling the Yahoo Application State Plugin by going to this page "about:addons" and selecting the tab "Plugins" then disable the plugin.

If you want to stop Yahoo! messenger from auto-loading, that is fairly easy, either by finding that option in the application, or using a utility such as AutoRuns which is available on Microsoft's site: [http://technet.microsoft.com/en-us/sysinternals/bb963902.aspx Autoruns for Windows] As far as I know, the ability to set the order of those programs that do start has never been included with Windows, even though users often would prefer one application to start before another. Doing a little web searching, I see a variety of utilities to do this. I haven't tried any of them myself, so please read up a bit on them before downloading. Here's one that has been around for a while: Startup Delayer (r2 Studios) * CNET: [http://news.cnet.com/8301-13880_3-10145143-68.html Free program brings order to Windows' startup chaos | Workers' Edge - CNET News] (2009) * PCWorld: [http://www.pcworld.com/article/231470/startup_delayer.html Startup Delayer | PCWorld] (2009) * Product page: http://www.r2.com.au/page/products/show/startdelay ''Note: I saw a very similarly named product that was released a couple years later. It is "ad supported" so that probably is less appealing.''