Included CMS files
To learn more about the order in which stylesheets are attached to CMS content, check out this article.
jQueryjQuery is automatically included in the head tag of every HubSpot template. It is rendered as part of the standard_header_includes HubL variable. You have the ability to choose between the latest version of jQuery 1.11.x or version 1.7.1, in Settings > Website > Pages. If you choose to use the latest version of jQuery, you can also choose to include a jQuery migrate script for backwards compatibility with older browsers. Additionally, you can choose to load this library from your footer.
public_common.css is a file that is included primarily for the HubSpot app navigation. It includes various animations used throughout the app, as well as a few snippets of code to style universal HubSpot elements such as blog featured images and bread crumb navigations. You can view the file, here.
Layout.css (fomerly known as required_base.css) is the file that is responsible for styling HubSpot's responsive grid. This file is always automatically included in any drag and drop template. It is not included by default in custom coded templates.
In addition to the responsive grid CSS, the file includes some classes that can be used to show and hide elements at different viewports. You can view the file, here.
HubSpot Tracking Code