What I think: Mistakes that designers make in flat design
Bad Screen - Bad Website
First of all I noticed that some websites use colors that don't work well on screens that are a bit cheaper or just not calibrated. These websites contain elements that have very similar backgrounds and therefore it becomes hard to differentiate between them since no shadows, thin borders or other useful separators are used in flat design. I think that you really should make sure that your website's contrasts work well on expensive and basic screens.
You can't just make a skeuomorphic design flat
I also noticed that several old websites were redesigned in order to match the flat design trend. Here comes the problem: The designers were too lazy and just removed all shadows, borders and gradients from the website. In addition they added some extra margins and extra padding. And do you know what that means? It's a usability disaster!
You can't just do that. If you want to "flatten" your design, you have to completely overthink it. Some element-positions don't make sense anymore as soon as you flatten the design. What do you have to do then? Hell yeah, you have to restructure your design.
You're makin' it too simple
I usually don't like to say that something is too simple, but now I have to. In flat design a user still has to be able to differentiate between a message, plain text and a button. What the heck are you thinking when you create user interfaces like that. Did you think that a user interface works better when everything looks the same? Nope. It works well when you can match different UI items because they have a similar base design.
Are you designing for the client or for yourself?
I would like to emphasize the fact that lots of web designers focus on making designs look good. What these designers usually completely overlook is that the user experience can be horrible. Especially when we look at flat design you have to focus on UX. Lots of flat websites look fantastic but are either slow, hard to navigate, not compatible with older browsers or just have no understandable user interface.
Summary
As you can see, there are lots of things that you must pay attention to in order to make a useful flat website. Do you agree with me? Write a comment and share your opinion.
