Websites generally don’t render same in all browsers. Therefore, web designers generally need to code their webpage accordingly. But the problem still persists because none of the most popular WYSIWYG editors generate 100% W3C standard code. The newer the standards, the less likely the code will meet those standards. Dreamweaver produces the most correct code while Front Page is the worst of the lot because it been a Microsoft product does the best job and Front Page the worst job. It’s not surprising that FrontPage, which is a Microsoft product, writes code almost exclusively for Internet Explorer. Hand coding does the job to a large extent but still not a guarantee as hard coding requires extensive knowledge of CSS standards.
Another problem is that a lot of the fancier and nicer features available are not universally supported by all web browsers. Many web designers choose to ignore the 35% of web surfers so they can implement the effects.