I get this error many times a day showing up in my event viewer. It generates 404's. I have never actually seen it when browsing the site and never had anyone contact me about getting that error either. I am trying to decide if it is something serious or just normal behavior because a search engine is crawling the site or something. Should I be concerned?

Event code: 3005 
Event message: An unhandled exception has occurred. 
Event time: 10/29/2013 7:46:55 AM 
Event time (UTC): 10/29/2013 11:46:55 AM 
Event ID: 770a2052e5f64d1d9bced11f85dc5258 
Event sequence: 3663 
Event occurrence: 92 
Event detail code: 0 

Application information: 
 Application domain: /LM/W3SVC/5/ROOT-6-130274824589807154 
 Trust level: Full 
 Application Virtual Path: / 
 Application Path: C:\webs\GregHowlett.com\ 
 Machine name: XLHOST-OF7SCMKU 

Process information: 
 Process ID: 5492 
 Process name: w3wp.exe 
 Account name: IIS APPPOOL\GregHowlett.com 

Exception information: 
 Exception type: HttpException 
 Exception message: Session state is not available in this context.
 at System.Web.HttpApplication.get\_Session()
 at ASP.global\_asax.Application\_AcquireRequestState(Object sender, EventArgs E)
 at System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
 at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

Request information: 
 Request URL: <http://www.greghowlett.com/WebResource.axd?d=eaEsW1VJ0NkQAOZyGROQvoqBSuXiiNQEj5h5BFT5JhWHeRYzpsB3S3kQNwRnDTTsqdN4g096MEjl2bD9ksb7BYVHe4qsARUqLIF3iTli30E1&t=635090765518590119> 
 Request path: /WebResource.axd 
 User host address: 41.71.154.2 
 User:  

 Is authenticated: False 
 Authentication Type:  

 Thread account name: IIS APPPOOL\GregHowlett.com 

Thread information: 
 Thread ID: 58 
 Thread account name: IIS APPPOOL\GregHowlett.com 
 Is impersonating: False 
 Stack trace: at System.Web.HttpApplication.get\_Session()
 at ASP.global\_asax.Application\_AcquireRequestState(Object sender, EventArgs E)
 at System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
 at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

Custom event details: