I was wondering how binding my websites Terms and Conditions are.
I am in California. I'm starting to sell to the U.S. and then Canada, and then the whole EU.
Your terms and conditions must comply with the laws in:
If they do they will generally be enforceable; if they don't then they will not be enforceable and you may be exposing yourself to civil and criminal sanctions. While not immediately relevant to you, Australian Consumer Law has such sanctions to goods sold into Australia from anywhere in the world; I am not familiar with other jurisdictions.
With respect to your comment that you will not accept returns or refunds, this would expose you to potential fines in Australia of $220,000 for an individual or $1,100,000 for a corporation - under Australian Consumer Law returns and refunds are a consumer right. I strongly suspect that most of the jurisdictions you are selling into would take a similar position.
A general "catch-all" like "to the extent permitted by law" may reduce the risk of being prosecuted but it would not eliminate it entirely. Again, in Australia, the provision is that you must not engage in deceptive and misleading conduct - merely suggesting that you will not give a refund even with the limitation above - may still be deemed "deceptive and misleading" if the court feels that a reasonable consumer might assume that they are not entitled to a refund.
You need professional legal advice on this.