it contains over 650 bugfixes including approximately 25 security fixes, and over 130 stability and dataloss fixes. In addition to these important security and crash fixes, 1.0.1 has many more fixes for standards support, UI correctness and polish, performance, and site compatibility :
Mozilla 1.0.1 is available for download now. This release is a bug fix and security follow-up to Mozilla 1.0.Download : Mozilla 1.0.1
Mozilla 1.0 users that have not already upgraded to Mozilla 1.1 are strongly encouraged to upgrade to 1.0.1.
Read the release notes for more details.