the page was builded using css and html

You should use <main> tag it is semanticly important. Every page should have <h1> tag because it is important for screen readers. If you want to add <h1> tag but making it only visible for screen readers you can use something like this.

 .sr-only {
        position: absolute;
        width: 1px;
        height: 1px;
        padding: 0;
        margin: -1px;
        overflow: hidden;
        clip: rect(0, 0, 0, 0);
        border: 0;
      }

Happy Coding 😊