How do I get previously opened site url in sharepoint 3.0?

I would like to get in my custom webpart an url address of the site which I was opened just previously before I get to current site(th开发者_运维知识库at with my webpart)? How can I achieve this?

Plain ASP.NET Method of getting the Referrer will work for this.You can easily do this with the Request.UrlReferrer