This is because the server control tags were not converted into their respecting HTML element tags by ASP.Net. This happens when ASP.Net is not properly registered with IIS.
.Net framework provides an Administration utility that manages the installation and uninstallation of multiple versions of ASP.NET on a single machine. You can find the file in C:\WINNT\Microsoft.NET\Framework\v**\aspnet_regiis.exe
use the command: aspnet_regiis.exe -u ---> to uninstall current asp.net version.