CMS Made Simple Forums

this might help: http://docs.cmsmadesimple.org/upgrading/old-versions

1.2.1 is from 2007. Countless hours of development have gone in to the project since then. Well worth upgrading if only for bug and security issues. Besides 1.2.1 is unsupported now.

There is a help doc on moving too:
http://docs.cmsmadesimple.org/moving

Let us know if you get stuck.

Re: I want to know if I download the most current version... will I have issues with my website working on this version?

Yes, if you don't do it correctly.

Depending on your site and how simple or complex it is it may be worth doing a clean install of the latest version of cms and copying the content across manually.