How to remove responsive features in Twitter Bootstrap 3?

Answer

To inactivate the non-desktop styles you just have to change 4 lines of code in the variables.less file. Set the screen width breakpoints in the variables.less file like this:

// Media queries breakpoints
// --------------------------------------------------

// Extra small screen / phone
// Note: Deprecated @screen-xs and @screen-phone as of v3.0.1
@screen-xs:                  1px;
@screen-xs-min:              @screen-xs;
@screen-phone:               @screen-xs-min;

// Small screen / tablet
// Note: Deprecated @screen-sm and @screen-tablet as of v3.0.1
@screen-sm:                  2px;
@screen-sm-min:              @screen-sm;
@screen-tablet:              @screen-sm-min;

// Medium screen / desktop
// Note: Deprecated @screen-md and @screen-desktop as of v3.0.1
@screen-md:                  3px;
@screen-md-min:              @screen-md;
@screen-desktop:             @screen-md-min;

// Large screen / wide desktop
// Note: Deprecated @screen-lg and @screen-lg-desktop as of v3.0.1
@screen-lg:                  9999px;
@screen-lg-min:              @screen-lg;
@screen-lg-desktop:          @screen-lg-min;

This sets the min-width on the desktop style media query lower so that it applies to all screen widths. Thanks to 2calledchaos for the improvement! Some base styles are defined in the mobile styles, so we need to be sure to include them.