1, as the friend above said, you have to check with the competent department. A real enterprise has many competent departments, such as industry and commerce, taxation and so on.
Just because the webpage can't be opened doesn't mean that people are an informal enterprise, and the network needs to be maintained. Maybe their network was being maintained when you checked. Shanghai company or Shenzhen company, this does not mean whether the company is formal: for example, the company is a Shenzhen enterprise and its branch in Shanghai is in the preparatory stage, so a branch like this can only use the business license and letter of introduction of the head office, because the branch to be established has no official seal and business license. This situation can also be explained.
The best way is to go for an interview when it is convenient for you in the past, just to see the company. Pay attention to the following questions during the interview: Take a look at the treatment of people with your education level in the market at present (you just graduated, you should estimate according to your graduation level. Generally, in Shanghai, Big Ben just graduated and joined the company. 1200-2000. College is 800- 1500). If the terms offered by the other party are excellent, I suggest you think twice. Nothing for nothing. Don't covet so cheap. No boss is stupid enough to give 3000 yuan a month to support a person without any work experience.
It's not very nice, but it's my experience in finding a job several times. I hope it helps you.