UX rule of thumb #1: Keep it clean.

Nothing gives users a headache faster than an overly busy (that is, cluttered) user interface. You may have heard of the expression less is more—and this expression certainly applies to UX design.

People feel like they have no time to do anything—and if doing something makes them feel like they are wasting their precious resource (that is, time), they become unhappy faster than you can count to 10. How does this relate to this first UX design principal? If there is a lot to look at on your page, they don't know where to start looking—and if they can't make sense of what they're looking at in short order, then you guessed it: they become unhappy. 

Clutter is almost never a good thing. Think of your bedroom or kitchen. Are you happier when it's tidy and everything has a place and purpose, and you can easily and quickly find what you're looking for? Or are you happier when you waste 5 minutes looking for that spatula to cook your breakfast that you barely have time to eat? The answer, I hope, is obvious. Visitors to websites think the same way.