Single login for all stores

Nop-Templates   provide a very good explanation in their blog

I have setup installation as per give blog.

How to set up multi-store. For example, we have two stores: www.store1.com and www.store2.com
Step 1. Upload and install the site on www.store1.com. This is only place where nopCommerce files and DLLs will be stored.
Step 2. Go to the control panel of "www.store2.com" (your hosting control panel, and not nopCommerce admin area) and ensure that all requests to "www.store2.com" are forwarded (not redirected) to "store1.com". Do it using CNAME records. This step is very important.
Step 3. Go to the control panel of "www.store1.com" and configure a domain alias for "store2.com". This step could be complex for some users. Just ask your administrator to do it if you experience any issues. Once it is done, when you open "www.store2.com" in your browser, you should see the content of "www.store1.com".


But still single login for multiple stores will not work on all browsers.
It  will work only IE9,IE10

For Example,I have login on www.store1.com then go to the www.store2.com and try to logoff i will not working in any browser.

I have login on www.store1.com then go to the www.store2.com it should be login but it will not working in FF,Crome and Safari browsers.

Can you please help me how to resolved this issue.

Actually SSO (single sign on) is not supported and won't work even in IE. You can vote for this work item here (some details on how to implement it is also on this work item page)