We try to notify this list when API changes are made in Drupal 7, so contrib and custom developers have a chance to fix their code before they have the pain of figuring out why it's broken.

(issue) Contrib modules should not use drupal_add_js() for core JavaScript files (which are all now packaged as libraries). Instead, use drupal_add_library(). Failure to do this can mess up the weighting of javascript files. This is true of any JS file that is included in a library: use the library to load it.

You may also be interested in general JS/CSS loading upgrade information, and also in the D7 Javascript Handbook Page.

Thanks,
-Randy

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Randy Fay
Drupal Module and Site Development
randy@randyfay.com
+1  970.462.7450