Check whether an object can perform a state transition before calling it. can_transition_ab? only verifies that a matching transition exists; validations may still block it.

Browsers may prompt to save passwords on login forms; setting autocomplete="off" on the form suppresses that prompt.

Very large forms can become unresponsive on iPad, with touch controls taking seconds to react. Showing only a limited set of inputs at once avoids the slowdown.

ActiveSupport::Memoizable can return wrong results when a memoized method is called with arguments, because true may trigger recomputation instead of being passed through.

jQuery 1.7 introduces on and off for event handling, deprecates bind, delegate, and live, and improves delegated event performance.

Downloading a remote file in Ruby can be done with open-uri; HTTP Basic Authentication credentials work when the source is protected.

Haml can render multi-line Ruby code with the :ruby filter when puts sends generated output into the template response.

Show me the page can fail to launch a browser window when launchy is outdated; upgrading to a newer version resolves the error.

Fresh Rails 3.1 apps can fail on boot when ExecJS cannot locate a JavaScript runtime, and adding a runtime gem to the Gemfile removes the error.

Persistent sign-in via remember_token keeps users logged in across browser restarts, while logout invalidates every matching session immediately by rotating the token.

MySQL character set defaults on Amazon RDS can require a custom parameter group and instance reboot to take effect.

Windows web fonts often render poorly because embedded hinting is weak; replacing it with autohinted font files improves readability across browsers.

A VirtualBox guest can be reachable on its own LAN IP by switching the adapter to bridged networking, enabling HTTP, SSH, and other direct connections.

table-layout: fixed makes a table divide its width evenly across columns, avoiding uneven sizing when equal column widths are needed.

cucumber fails because cucumber.yml cannot be parsed; removing rerun.txt in the Rails directory often fixes the invalid rerun state.

Solaris does not provide /proc/cpuinfo; psrinfo -v is the standard way to inspect processor status and speed.

Stub a method on every instance of a class to control behavior in tests, using stub_any_instance, any_instance.stub, or allow_any_instance_of.

screen can fail with “Cannot open your terminal '/dev/pts/0'” after switching users in the same session; owning the shell correctly or reconnecting as the target user avoids it.

MySQL table collation and default character set are available through SHOW TABLE STATUS and SHOW CREATE TABLE; individual columns can still use different encodings.

MySQL character-set mismatches cause garbled text and inconsistent comparisons; SHOW VARIABLES LIKE 'char%' and my.cnf settings reveal and change the server defaults.

Shareable Git changes can be turned into patch files and reapplied in another working tree or repository. git apply stages changes as edits; git am recreates commits with messages.

Force a fixed client IP in Cucumber scenarios when request-dependent code needs predictable behavior.