If you have a black H by your hub it means that it is "featured" and will show up on your home profile page.
If the H is orange then if was determined to not be featured due to a poor quality of content. My very first Hub is not featured and I believe it is because I didn't use multiple text boxes and have no displayed pictures. I've found that if you follow the prompt that wants you to write 700 words and one picture minimum, and have few grammatical errors, then it will most likely be featured.
If there is a Blue H by your hub then according to HubPages it means "This Hub is not Featured because it does not receive sufficient engagement. Try updating the Hub with recent information and descriptive, search-friendly sub headings."
You can find the above information on your "my account" homepage. Hubpages has provided a key to their symbols at the bottom of your list of Hubs.
I could be wrong, but I'm not sure that the public can see your non-featured hubs anymore. However, they still factor them into how many total Hubs you've published.
I love this new system because it insures, more than ever before, that the HubPages community remains strict on their quality standards. We do not want this site overrun with spam and poorly written paragraph long hubs.