One thing I do while developing Drupal sites is make frequest trips to the "Recent Log Entries" page (admin/reports/dblog) to see what kind of trouble any custom code (or rouge themes and modules) I've added is causing. It is a quick "sanity check" to make sure things are moving in the right direction.

A pet peeve of mine when using a custom theme has always been the "page not found" log entry for the "favicon.ico" file. When using a custom theme (or an overridden favicon.ico file), while Drupal outputs the correct path for the link tag that specifies the file, some browsers still look for the favicon.ico file on the root of the web site. Normally, I "fix" this issue by making a duplicate of the favicon.ico file and placing it on the root of the site.

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