Mobile First CSS with Boostrap 2.3

grid.less

// Bootstrap's fluid grid 
#grid > .fluid(@fluidGridColumnWidth, @fluidGridGutterWidth);

index.less

// Bootstrap modules
@import "bootstrap/less/variables.less"; 
@import "bootstrap/less/mixins.less";
@import "bootstrap/less/reset.less";
@import "bootstrap/less/scaffolding.less";
@import "bootstrap/less/type.less";
@import "bootstrap/less/buttons.less";
@import "bootstrap/less/forms.less";
@import "bootstrap/less/tables.less";
@import "bootstrap/less/layouts.less"; 

// Layout
@media (min-width: 768px) {  
	@import "grid.less";	
}