SwitchUp SwitchUp Ranked Best Coding Bootcamps 2025

ActionController::UnknownFormat for css files not found

Altcademy Team wrote on 7 February 2018

You have to catch this error yourself.
In application.rb
class ApplicationController < ActionController::Base
  rescue_from ActionController::UnknownFormat, with: :raise_not_found
  private
  def raise_not_found
    render text: 'Not Found', status: 404
  end
end

Learn web development online

Cohort 111 begins on March 2nd, 2026

Most Popular

Most Popular7 Courses
Front-end
Back-end

Full-stack Web Development

Learn full-stack development with HTML, CSS, JavaScript, React, Ruby and Rails, Computer science fundamentals & programming skills.

VIEW DETAILS

Upgrade FSWD to include Python, Data Science, AI Application, TypeScript and more.
3 Courses
HTML
CSS
JavaScript

Front-end Web Development

Learn front-end development with HTML, CSS, JavaScript, and jQuery. Computer science fundamentals & programming skills.

VIEW DETAILS
2 Courses
Database
API
Testing

Back-end Web Development

Learn back-end development with Ruby and Rails, M-V-C. Computer science fundamentals with practical programming skills.

VIEW DETAILS

Trusted by

Students and instructors from world-class organizations

Imperial College London
Carnegie Mellon University
City University of Hong Kong
Hack Reactor
Cisco Meraki
University of Oxford
Swift
Bazaarvoice
Waterloo
Uber
AtlanTech
Tumblr
Boston College
Bombardier Aerospace
University of St. Andrews
New York University
Minerva Schools at KGI
Merrill Lynch
Riot Games
JP Morgan
Morgan Stanley
Advanced Placement®
Google
KPMG
The University of Hong Kong
University of Toronto
SCMP
Moat
Zynga
Hello Toby
Deloitte
Goldman Sachs
Yahoo
HSBC
General Assembly
Tesla
McGill University
Microsoft
Logos provided by Logo.dev

Join the upcoming Cohort #111

Enroll for March 2nd, 2026