I follow the instructions from SiteFinity docs to set up my web.config to a medium trust.
I tested my site with the link Mosso provided me, and discover if you place trust level = medium in your web.config file the site will break. Leave that line out, because Mosso is a modified Medium Trust. My site work fine in medium trust after removing that line.
The sitefinity site drops out the server memory after so many minutes pass by with out a visitor. To keep it memory do the following.
Steps to fix the slow start up:
1. Log into Mosso/Rackspace panel for your website.
2. Select the Feature tag for your site
3. Under Scheduled Tasks, Add New Task
4. Task Name field: Keep Alive
5. Email address for the task results, note I use my yahoo account and send the email to spam.
6. Set Command Language to http
7. Set Command to Run to you home page of your site
8. Set Repeat by to Minute
9. Set Frequency to Every 15 mins.
This will increase you site load time. You can adjust the frequency until it loads quick every time.