jQuery done() and then() differ in promise chaining: then() waits for returned promises, while done() ignores them and can resolve too early.

Large XML imports can exhaust RAM with Nokogiri’s DOM parser; SAX parsing streams data and avoids building the full tree in memory.

Geordi 6.0.0 keeps geordi commit running when some projects are inaccessible and drops VNC browser support and @solo serial execution.

Build static pages with Rails-like comforts such as HAML, SASS, helpers and partials, then compile everything to plain HTML and CSS.

NewRelic monitoring can be restricted to selected Rails hosts by checking the current machine name before enabling monitor_mode.

Memcache nodes can degrade after long runtimes as slab allocation becomes tuned to stale access patterns, increasing evictions and lowering hit rates.

Starting an existing vagrant up can fail when VirtualBox host-only networks conflict over DHCP settings. Versions before 2.2.9 need a Vagrantfile workaround.

HTML semantics improve readability, accessibility, and parser interpretation by matching elements to meaning, while HTML5 sectioning and text-level elements add structure and built-in behavior.

Dual-screen presentations on Linux can keep speaker notes or a projector preview visible without cloning displays. x11vnc and a VNC viewer provide a local preview of the second screen.

Angular ngSrc leaves src unchanged when the bound value becomes empty; using //:0 forces an invalid blank image source so the browser clears it.

Curl sends and stores no cookies by default; -c and -b let you save, reload, or manually supply them for repeated requests.

Local SSL development with Thin avoids mixed-content and redirect issues while testing force_ssl on localhost using a self-signed certificate and separate HTTP and HTTPS ports.

Apache can be awkward for reverse proxying, especially with Digest Authentication and HTTPS passthrough; nginx offers a simpler setup for forwarding requests to another host.

mysql2 0.3.13 can fail to compile on older Ruby 1.9.3 patch releases in rvm, causing an undefined symbol error; pinning 0.3.11 avoids the issue.

LoadError occurs when a Ruby gem is required outside Gemfile or .gemspec; adding its install path to $: allows temporary loading for debugging.

Rails secrets and other configuration values can be read inside webpack bundles with rails-erb-loader, enabling environment-specific client-side settings without hardcoding them.

Encrypted connections between Rails and Amazon RDS MySQL protect sensitive data in transit. mysql and database.yml can be configured to require SSL end to end.

Specs can stall for 30+ seconds when SOLR connections are left open and the pool is exhausted. Lowering the old-connection timeout reduces the delay.

Rails or Rake can report missing gems even when they are installed; wrong Bundler configuration or release-directory leftovers often redirect gem lookup to the wrong place.

AJAX downloads fail because browsers try to render files instead of saving them. Exclude download links from Unpoly link handling and use Content-Disposition: attachment or download.

Ruby charting library for Rails that generates PNG graphs with themes, multiple series, and automatic sizing for large datasets.

Speeds up navigation by keeping the page alive between link clicks, avoiding repeated JavaScript and CSS recompilation while replacing the body and title.