Most of these are unnecessary, sure. That aside, I wanna focus on the clearfix() one real quick. For stuff like this, just have a helper class. Otherwise, you're copying this code snippet into your compiled stylesheet every time you use the mixin.

Instead, if you just make it a class (something like...

...)

you can use it like <div class="some-element clearfix">foo</div>, and you're only writing the rule once.

You should take a look at implementing Autoprefixer into your workflow. Doesn't matter if you're compiling using grunt/gulp or a GUI like Codekit, it's simple to set up and would render 4/6 of these unnecessary.

Or you could just use Bourbon.