If you want to try yahoo messenger 11 you can download at the website here: http://messenger.yahoo.com/beta/win but if the messenger downloaded from the link is online installer. It mean your computer must connected to internet when install this software. To save your time to install this yahoo 11 version you can download offline installer yahoo messenger 11. You can download the offline installer from the below list.
Yahoo Messenger 11 Offline Installer (All language Version) Download link Offline installer yahoo messenger 11 US English version: ymsgr11_us.exe
Other downloads link offline installer Yahoo Messenger 11 for international users