Let me start with a small clarification -- Telerik.Charting.dll is part or RadControls for ASP.NET AJAX Q1 2008 SP1, which is rather old now. Still, I believe you have your reasons to use it, so my answer will target this version, let me know if this is not the case.
The RadControls setup installs the Telerik.Charting assembly in machine's GAC. When you create a web site and drag RadChart to the design surface, Visual Studio will add a reference to Telerik.Charting in web.config file. When deploying the web site you will need to copy Telerik.Charting.dll to the web site Bin
folder. Note, that each version of Telerik.Web.UI will work with a specific version of Telerik.Charting, so you need to copy the very same version of the assembly as the one mentioned in web.config file ex. 18.104.22.168. Then you can remove the web.config registration.
Alternatively, you can keep the web.config registration and install Telerik.Charting to the server's GAC. Installing manually an assembly in GAC is as simple as dropping the assembly in c:\Windows\Assembly folder.
Finally, I would like to note, that as of RadControls for ASP.NET AJAX Q3 2008 Telerik.Charting.dll does not exist as a separate file, so you do not have to manage such problems.
the Telerik team