Blogging can be both hobby and business. The most important question is if it taxable or not.
Blogging as a hobby
Blogging is considered a hobby if the blogging is not aimed to make profits over time.
Income from hobby is not taxable and you also do not get deduction for costs related to such activity.
Blogging as a business
If the blogging is aimed to give income, it is business. All income is taxable, and deductions can be obtained for costs.
Blog on foreign server
Many blogs via foreign server. Where the blog is physical placed has no influence, tax rules are determined by which country the blog is operated from.
Tax and VAT
Promoted products and gifts received with economic value, are tax and VAT obligated.
Some bloggers receive gifts they have not asked for and do not want. If the gift has been thrown or sent back, it is not VAT or taxable. This must be documented by listing what is thrown or returned.
This info is valid directly in Norway, please check your own country law.