Web application projects, in use since VS 2005 (I think), do not support the ProfileCommon class. There are a couple of free third-party projects that I know of that solve the issue, but AFAIK
only one of them works seamlessly with VS 2008: WebProfileBuilder. You can Google that and download it from the msdn code page. Install instructions are provided in the readme.txt file included in the download package, but to sum up:
1. Run the installer.
2. Add this Import statement to your project file. (see special notes below)
<Import Project="$(MSBuildExtensionsPath)\WebProfileBuilde r\WebProfileBuilder.targets" />
To do step 2 just open the .csproj file (or .vbproj if you use vb
projects), search for Import Project, and add the aforementioned statement just below an existing one.
Note that, strictly speaking, ProfileCommon will still be unavailable, but you can replace all functionality by doing this:
//ProfileCommon profile= this.Profile; // doesn't work on web app projects
WebProfile profile = new WebProfile(HttpContext.Current.Profile);
In some versions, WebProfileBuilder can't create the required webprofile.cs file; yet, if you create a dummy file by such name (with notepad.exe, for instance) in your project's root folder WebProfileBuilder will overwrite the file's contents.
Hope this helps.