I would like to know if you can add more than 25 websites
No you can't do that - as a premium member you are only allowed 25 free hosted sites and 25 hosted sites for domains you own - for a total of 50 sites - you can't get more.
If for some goofy reason you need more then that you would need to find hosting for those additional sites else where.
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What happens after you reach your 25 website maximum?
I would like to know if you can add more than 25 websites
No you can't do that - as a premium member you are only allowed 25 free hosted sites and 25 hosted sites for domains you own - for a total of 50 sites - you can't get more.
If for some goofy reason you need more then that you would need to find hosting for those additional sites else where.
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sorry, you don't have to buy the domain from WA but it helps
Robert