Forget about cosmetic web design trends, today's latest and greatest trendy cool cosmetic effect soon becomes over-used, naff, cheesy, and so 'yesterday' or 'last year'.
There are some important web trends you should keep in mind:
1. Web browser trends, what are people using to browse the web and your website, (e.g. recent important trends include iPhone and netbooks, very small laptops, and the associated
web design screen sizes involved for these devices)
2. Web usability trends, thankfully these don't change too often, the basic ways we navigate through sites, the way we add products to baskets and checkout etc, but these are important, because if your site works like other popular sites users visit, users will already be familiar with your site too. Follow the accepted de facto norm in this case, don't opt for some new user interface that is unfamiliar and unfriendly for your users.
3. Search engine trends. Search engines are continually evolving their algorithms so if search engine ranking and traffic is important for your site, you need to keep up with this and treat it as an ongoing process.