Added "global max width" and fixed a syntax error
Added global variable for html font reset
Some major changes: added default parameters to the mixin 'background-placeholder', added a 'property' mixin from @borodean that allows for dynamic properties, added a rem, em, and % calculation mixins, and a mixin for a horizontal row.
Included the global html reset variable and moved the html block to a better place in the reset.
Added mixins for min-width, only screen, portrait and landscape
Fixed opacity syntax errors and order of operations.
Added new calculations for rem font size, replaced the two line-height mixins with one that accounts for all browser behaviors