Stupid question when designing a site does the customer supply the content and photos?
Depends, really, on the situation and what’s in the contract.
If you’re just designing the site, but not building it, then I think using place-holder text and images is pretty standard, but this isn’t something I do, so don’t take my word for it. 
If you’re actually building the site, then you need to work out with the client beforehand who is responsible for what. Are they going to supply the content, or do they want you to do it (or employ a content writer on their behalf)? I work mostly for small businesses, and as I always point out, they know far more about their business than I ever will, so it would be daft for me to write the content. Getting them to agree to supply the content is usually pretty easy; getting them to actually supply the content sometimes feels like getting blood from a stone. 
As far as photographs go, I enjoy photography, so if the client doesn’t have suitable pictures, I’m happy to provide them. If it’s for a commercial site, I charge extra; if it’s for a not-for-profit I just throw them in free as a goodwill gesture.
Hope that helps.
You will need some idea of what sort of content you need to design for, otherwise you are designing in the dark!
Yes when you are designing the site then customer will supply you the content and images.
It really does depend on the contract, always clarify SCOPE and EXPECTATIONS before accepting a job.
For example, a client may want small commerce site that wanted their products to be displayed with a certain look and feel, as such the client may provide text content , but might want you to do the product photography. Again each situation is different… don’t be afraid to scope/price and delegate accordingly.
It all depends on a project/client. Howeve i would say that most of my wroks the content was provided by the client.
Depends on your client, you should first ask if they will be supplying content and images before quoting them.