For a repro of a problem my customer has I ran into the following issue when installing Citrix Web Interface 5.3 (I know that 5.4 is available but for this issue I needed 5.3 
).
After installing default IIS with the IIS 6 Management Compatibility I got a nice blank webpage when visiting the Citrix Web Interface.
When checking the installation/configuration of IIS I noticed that I missed some features in the installation of IIS.
Web Server Common HTTP Features
- Static Content Not Installed
- Directory Browsing Not Installed
- HTTP Errors Not Installed
After installing these components the problem of my blank webpage were gone. 