Error about import javax.servlet.* in eclipse

Today in order to debug my servlet, all of a sudden, I found all the servlet under the site all wrong, carefully look, it is import javax.servlet.* here a mistake.

Then I looked up some information on the Internet, only to find that I had to reinstall the Tomcat server a few days ago, is this apart from the problem?

So I reconfigure myself to add my newly installed Tomcat server to eclipse, but the error still occurs, and it doesn't matter to the server. But for the sake of me, I was building a project to rewrite a servlet, but this time I was not surprised, this time there is no error, but the previous site file error is a lot of. Why is this happening?

I think for a moment, may be the previous configuration of the server has not been deleted, really did not think wrong, and finally found that my previous server is all a red fork, only just configured that the server is normal. I then replaced all my sites with a new server. All forks are removed, oh, is not very simple.

Let me use a diagram to explain:

See all the Red forks

Step Two:

Select the server without the Red fork, it is OK, is not very simple.