Written material need not be entirely original to be protected. Where other written material is incorporated in the work and this 'secondary written work' is produced as a result of 'skill, judgement and labour' then copyright will be available to the author. Where the author is employed to write say a web page then copyright belongs not to the author but to the employer. This is a very real problem for web developers. Graphics can include computer generated shapes, photographs and even animated graphics.
Graphics are freely available on the web.
Some are free some are for sale. The first rule is always check the conditions before you use other peoples graphics. If you do purchase graphics check the license agreement. This agreement may have limitations on the use or any adaptation of the graphic. Simple drawings may attract copyright.