InfoPath 2010 Contact Selector Control. Unable to add

This contol cannot be added through the custom control wizard. To use this control, go to the controls gallery on the home tab.

Solution:
In Infopath 2010 already exist. the control Called Peopl/Group Picker. You can add this control and set Sharepoint server.

If you want same problem in Infopath 2007 use this link.
http://blogs.msdn.com/b/infopath/archive/2007/02/28/using-the-contact-selector-control.aspx

How to Install VSTA (Visual Studio Tools for Applications)

I was searching for an installer for VSTA (Visual Studio Tools for application).

Solution :
Control Panel ---> Add or Remove Program --> Office 2007 -- > Change -- > Add or remove features

Under Microsoft Info Path  Visual Studio Tools for application and Choose Run as My Computer. Continue.
After successful completion restart your computer.

Error : Session state can only to be used when enable sessionState is set to True

Session state can only to be used when enable sessionState is set to True, either in configuration file or in the page directive. Please also make sure the System.Wbe.SessionStateModule or a custom SessionState modle is included in the <configuration>\<system.web>\<httpModule>.

Solution :
Step : 1
 <page enableSessionState="true">.
Step : 2
<modules runAllManagedModulesForAllRequests="True" >.

Step : 3
remove the line if available
<modules>
           <remove name="session" />
</modules>

Error : The Configuration section cannot be used at this path. Your Current Security setting do not allow this file to be download.

The Configuration section cannot be used at this path.This happens when the section in locked at a parent level. Locking is either by default(OverrideModeDefault="Deny"), or set exactly by a location tag with OverrideMode="Deny" or the legacy allowOverride="false"?

Error : The Configuration section cannot be used at this path. Your Current Security setting do not allow this file to be download.

Solution:
Open the applicationHost.config file

C:\WINDOWS
SYSTEM32\INETSRV\CONFIG\APPLICATIONHOST.CONFIG

And Change AllowOverride="true" instead of false on that file.