I have created 2 store and both store menu are different.
But when i open both store in same browser, then his menu conflict or change other store menu
Product description page details mixed both store.
how is got issue...
1. open both store in same browser.
2. open first store 1 product details page.
3.then open 2nd store 1 product details .
4. go to option 2 refresh it you will get menu and description have been changed.
When you use /?___store= a store cookie is set. Magento uses this cookie to distinguish which store view you are on so you can only have one of these set in your browser.
When you start browsing around, one of these will take priority, which is why it looks like your store suddenly switches to the other store, when actually you have changed the store cookie for the Magento site.
Does that make sense?