Array values in Rails HTML options become space-separated strings, making class helpers accept multiple CSS classes without manual joining.

Temporary browser state survives reloads and accidental refreshes but stays separate for each tab or window; sessionStorage is string-only and not always available in private browsing.

Set application-wide defaults for URL generation in Rails instead of duplicating them in multiple places as issues arise.

<sub> and <sup> often break line height in email layouts; setting line-height: 0 with mso-line-height-rule: exactly keeps superscripts and subscripts consistent across clients.

Prevents duplicate command instances with the same arguments from running at once, useful for cron jobs and other repeated tasks.

Async Unpoly compilers cannot return destructors directly; up.destructor works, but detached elements can leak memory unless attachment is checked after await.

Create Markdown links to cards in other decks with a bookmarklet that copies the current card title and path into link format.

ActiveRecord migrations can break when STI models are referenced directly; embedding model classes in the migration and overriding find_sti_class and sti_name keeps type lookup working.

Many development tools consume inotify watches until the operating system limit is reached. A /proc scan identifies the process that uses the most watches so the limit can be raised or the culprit adjusted.

A framework for organizing technical documentation around four user needs: tutorials, how-to guides, reference and explanation.

Efficient ways to create DOM test fixtures for Jasmine, from HTML parsing and selector helpers to innerHTML, with readable structure and direct element references.

Using separate local hostnames avoids cookie clashes and logouts when switching between web apps on Rails development servers.

Keyboard shortcuts and layout options in DevTools speed up panel switching, drawer visibility, and workspace organization.

Chrome DevTools Layouts tab helps inspect and tune CSS Flexbox and Grid with overlays, badges, and visual controls for sizing, alignment, and nested layouts.

Unitless zero values are invalid inside CSS calc() expressions, which can cause ignored declarations and missing or unpredictable layout behavior.

Custom keyboard shortcuts in web apps can clash with browser and OS defaults, making features hard to discover and use. Consistent, discoverable bindings improve efficiency without breaking expected behavior.

Variable fonts can reduce file loads and broaden typographic control, but performance gains depend on how many font styles a site needs.

RubyMine can waste startup time by reopening the last project automatically, especially when switching between projects. Disabling that startup behavior and using the project chooser improves project switching.

Modern browsers run most ES6 features natively, but Rails asset pipelines can still fail when Uglifier cannot minify newer syntax.

Mixing optional positional and keyword arguments in Ruby methods can turn hashes or to_hash objects into unexpected keywords and raise ArgumentError.

includes can duplicate primary keys in ids when loading associated records, causing unexpected non-unique results; preload keeps the ids list stable.

Large Rails projects often duplicate date and datetime format strings, causing inconsistent output; named formats in Time::DATE_FORMATS and Date::DATE_FORMATS reduce repetition.

Sass 1.35.0 can suppress dependency deprecation warnings with quietDeps and limit warnings in your own code with silenceDeprecations.