Debugged! is the premier debugging suite for WordPress theme and plugin developers (although everyone is certainly welcome to it!). It provides a simple to use and unobtrusive debugging bar (the location and display of which is configurable) which will allow you to check system information, GET and POST variables, cookies, session variables and SQL queries at a glance, as well as providing a simple-to-use error checker and inline W3C validation.
Features
Keep track of Globals, SQL Queries, etc Easily check for and monitor PHP errors Easily run your site through the W3C Validator Configurable debug bar location and appearance 100% Translatable
Changelog Version 2.0.1 (June 29, 2013) * Updated headers to use sprintf * Added PHP and WordPress info to System Info tab * Minor compatibility fixes
Version 2.0.0 (May 7, 2013) * Updated backend framework * Rewrote plugin codebase * Added System Info tab
Version 1.4 (February 1, 2013) * Updated backend framework * Fixed bug with warning/validation classes on recent WordPress releases
Version 1.3 (October 30, 2012) * Fixed critical error with instances where there is only one PHP or HTML error
Version 1.2 (October 28, 2012) * Fixed minor CSS issues * Added text for situations when no errors are found
Version 1.1 (October 20, 2012) * Fixed error in jQuery scripts * Replaced all images with icon fonts * Minor code cleanup
Version 1.0.1 (September 24, 2012) * Fixed undefined variable error on login page
Version 1.0 (September 21, 2012) * Initial Release