Comment Issues

I am having issues with comments showing up on my blog postings. I've changed the background a few times recently, thinking maybe that was some of the issue. People told me they would try to comment, but they weren't able to. Now people have told me they have commented, but the comments don't show up after the postings. I have done a lot of research online but can't seem to find the problem. Have any of you had issues with comments on your blog, or problems posting comments to my blog? If you do post a comment, can you email me, too, and let me know that you commented? Thank you!