HttpPost error in mvc

Dear team,

I have asp.net mvc project when I use HttpPost  method for a action result. I got a error .

Discription: HTTP 404. The resource you are looking for (or one of its dependencies) could have been removed, had its name changed, or is temporarily unavailable. Please review the following URL and make sure that it is spelled correctly

Actually my purpose is when user select a dropdownlist selected item I need get the value pass to controller. I used Request, Request.Form,Form collection,Parameter. But I couldn't able the selected value to the controller. Everytime I got null value. And when use the HttpPost method I got above error If any body know the issue kindly help me. Actually I have entity model class for this purpose. But my dropdownlist situated under another model and here I am used via

public string IEnumerabletheme{get; set;}.

If have any idea for my error kindly helpme

Thanks & Regards

Rajeesh