本來服務器上運行的是asp.net框架版本是1.1，網站IIS運行一切正常，但今天有客戶需要安裝.NET 2.0版本；安裝了2.0版本後，服務器運行就出現Server Application Unavailable的提示，令人莫名其妙，查閱相關文檔，終於有了解決方法，原因是.net Framework 1.1和.net Framework 2.0有沖突。
具體錯誤信息會顯示如下：
Server Application Unavailable
The web application you are attempting to access on this web server is currently unavailable.Please hit the "Refresh" button in your web browser to retry your request.
Administrator Note: An error message detailing the cause of this specific request failure can be found in the application event log of the web server. Please review this log entry to discover what caused this error to occur.
查看Event Viewer,看到的錯誤為:
Error:Failed to execute request because the App-Domain could not be created. Error: 0x80070005 Access is denied.
解決辦法:在該web sites的virtual directory下,將Permissions設置一下,裡面應包含：
ASP.NET
IWAM_MachineName
Local_Service
Network_Service
System
而且權限要設置為write & read.
設置後,一切運行正常.
