Host to use Microsoft Visual SourceSafe or CVS on web hosting for development?
I would start with the question "Why VSS or CVS"? Is this because of a legacy reasons, or is it because you don't know other options?
If the answer is "because of legacy", then you don't have much choices. There are no cloud providers that offer VSS support, and the choices for CVS are not that great either. SourceForge.net still offers CVS support, and searching for "CVS hosting" also yields some results, but most are not well-known names with proven reliability and security.
However, given what your choices are, I would be quite interested to hear more details about a legacy project that uses both VSS and CVS. :-)
If, however, the answer is "because I don't know what else is there", I would strongly recommend to look into SVN, Mercurial or GIT. There are great cloud providers that offer support for these three ranging from free for open source projects to multiple tiers of paid support for proprietary projects. And it's quite easy to set servers for any of these three yourself. Not to mention that all of them are orders of magnitude better than VSS and CVS.
To give you a quick start, here's a short list of providers you can look at:
There are a lot more out there, with various pricing models (and reliability of course :-))
Update: If you are working on a web app, your web host dos necessarily have to support also the source control. You can have your sources (HTML, CSS, JS) in a separate version control host, and deploy to the web host only the final version of your work.