Please help me with the following questions:

1. It is a good practice to use mixed casing to denote HTML tags?

2. Web pages might look different in a browser from what they look like in a GUI editor.

3. In XML, you use the same syntax for specifying comments as you would for in HTML

4.Which tag enables to divide a Web page into sections?

5. Why my browser displays the message "HTTP 404 - File not found" when I click on a link in a Web page.

thanks for your help