If you are using 3.5 Extension in your website , you must pray that your hosting administrator , will not unistally 3.5 CTP preview and install 3.5 SP1 , everything will blow up, so here are the steps to solve that and let your old website works with 3.5 SP1 , which will be more faster than when we were using 3.5 CTP Preview :

1- Uninstall 3.5 CTP from your machine,

2- Download Full Package of SP1 (It will be faster from downloading 2.8 file ), size (237 MB): http://download.microsoft.com/download/2/0/e/20e90413-712f-438c-988e-fdaa79a8ac3d/dotnetfx35.exe , Then install it

3- Create a new ASP.Net Ajax Future Website , and use its web.config get the stuff you added in the old web.config and use assembly and httphandlers from the new web.config

4- Download and Install ASP.Net Futures: http://www.microsoft.com/downloads/details.aspx?FamilyId=9323777E-FE78-430C-AD92-D5BE5B5EAD98&displaylang=en

5- Add reference in your project for Microsoft.Web.Preview and this will added Microsoft.Web.Preview.dll

Now your website will work on any hosting environment has 3.5 SP1 , and it will be more faster.