I\'ve created a web service that other sites can use to store errors in my database. They can then come to my site to view their errors, search through errors, filter error
You will need to create a class that is serialisable designed to hold the sort of information that you wish to gather. Then create Static method on that class which will create an new instance of the class and gather up the info required.
Its would be this new class that would be passed to LogError.
You're not going to be able to serialize the HttpContext. Your best bet would be to create a custom class to encapsulate the information that you want out of the HttpContext and pass that into your WebMethod.