Trends are great, because they illustrate what we're aware of and what we're becoming capable of in the future, but they're also a good picture of what they're replacing; movements towards flat and minimalist designs show us that we may have been over complicating our web design, for example. Here are a few trends that should fade out when you're considering modern design in 2015, and why they're on the way out.

Trends that Need to End in 2015
  • Pop-ups, splash pages, and misleading landing pages. These aren't new, and in fact have been around since the technology to display them has existed, but that doesn't mean that they aren't a trend, and that people still don't use them. Even, which is a fairly popular news site you may have heard of, uses a splash page. They do this for a number of reasons, but the top association that users have with splash pages, pop ups, and even some landing pages, is that they're just there to sell a product, which they are. Landing pages need to be clear and concise, and as for pop ups and splash pages, the former needs to only be used for utility purposes, and the latter should probably just not be used at all. Avoid those two if possible. As for the landing page, keep it relevant. Otherwise, you'll redirect users away for your website.
Trends that Need to End in 2015
  • Skeumorphism. It's a complicated word that says “looks like a 3D object or surface,” and it gained popularity with the rise of iOS. Skeumorphism is most commonly seen these days in the “book shelf” presentation that some applications use to display books or magazines, but it's really everywhere, and it's officially been made obsolete by the movements toward flat design and Google's new Material Design aesthetic. Both can take advantage of the idea of creating a pseudo-3D space, but do not rely on the incredibly immersion-breaking CGI of false wood and metal to achieve that. On top of that, flat design and material design are easier to incorporate into a site in new and exciting ways; skeumorphism realistically has one mode, and that mode is looking increasingly dated with every passing day.
  • Loading a page down with videos. Some sites still do this one. A whole laundry list of YouTube videos will load on the sidebar of a page. Imagine a kid pressing every button on an elevator, and that's about as obnoxious as these video lists can be when they're all laid out at once, even if they aren't set to autoplay (which, in all honesty, they never should be.) The loading time of each of one of those videos is an unnecessary slowing point for both desktop and mobile browsers. Just avoid doing this one entirely.

Other trends, like the use of Flash, should be considered even more of an online dodo. It's good practice to look at popular lists of trends every year, and see what they could be replacing on your site.