Even if you are unsure and want to try it out while retaining your existing meta tags contribution there is a "2 minute test" instruction where you can try out KissMT without compromising your existing installation.
KissMT Dynamic SEO Meta & Canonical Header Tags
powerful seo meta tags & canonical elements in just 5 minutes.
Compatibility:
Oscommerce MS2.2, RC (all versions)
PHP 5.2+/5.3+ ( PHP 4 NOT supported )
MySQL 4/5
Download:
http://addons.oscommerce.com/info/7199
Credits: ( thanks to all the beta testers without whom the initial KissMT release could never have been so solid )
Special thanks to:
Tom aka tomh/perfectpassion, Graeme aka knott, ken aka ken44, James aka jwilkins
Thanks also to:
Wim aka Mister_dj, Onno aka Onnootje, John aka berkedam, Fabian aka proimage,
Daniel aka Morpheus1979, Marie aka mariemeh.
Recommendations:
We recommend the use of Ultimate Seo Urls 5/5 Pro as the perfect Seo Url addition to this contribution.
http://addons.oscommerce.com/info/6768
Header tags seo and other meta tag contributions:
Want to try this out but leave your existing meta tags contribution in place? Do the safe 2 minute test! ( documentation/2_minute_test.html )
Features:
Fast 5 minute install ( easy for beginners and experienced )
Dynamically generated meaningful meta tags with no complexity.
No core osCommerce file changes ( except replacing the <title></title> in the catalog files ).
Updates and upgrades with no core osCommerce file changes ( just replace the module directory ).
Compatible with highly modified sites. ( due to "no core osCommerce file changes" )
Modern Canonical elements, as recommended by Mat Cutts of Google, protecting you against indexed sessions ( osCsid ) and duplicate content.
Automated Meta titles intelligently built (to your specified length)
Automated keyword generation with stopwords removed. (multi language capable)
Automated description generation.
Automated meta title capitalisation excluding small words (multi language capable)
Highly efficient system using 2 queries maximum and none after cache load. ( so ideal even for the biggest shops )
Modern PHP 5.2/5.3 code
Error free with no deprecated code ( even on high error reporting E_ALL | E_STRICT )
Perfect for small and large shops ( due to efficiency )
No complex manual "fiddling" required. ( works out of the box )
HTML/XHTML output. ( easy to validate )
Performance output for testing & development ( or just to exemplify efficiency )
Extra features: ( requires additional install )
Admin based settings ( database install )
SEO Category content. Text content for every category page. ( also used in meta tags )
SEO Manufacturers content. Text content for every manufacturers page. ( also used in meta tags )
H1 tagged SEO automatic page titles. ( to your specified length )