I create a highly engaging website or web application by writing HTML and CSS from scratch, slice designs from Photoshop and/or Fireworks, and work closely with creative team to ensure visual requirements are met. I add interactivity to a website with Javascript (both vanilla and using frameworks).
I build RESPONSIVE websites using progressive enhancement (and sometimes graceful degradation, depending on the client's requirements) technique, supported by feature detection tool such as Modernizr as well as some well-known responsive frameworks like Bootstrap or Foundation .
I use Javascript and jQuery to add interactivity to websites. Fortunately I am lucky enough to have also used Backbone, Marionette, Underscore, Blaze, React, and Handlebars to make my coding more structured, efficient and easier to mainatin. Plus some additional tools: Require JS & Enquire JS.