The thumbnail of your website will be automatically generated and displayed next to your listing. Usually it takes a few hours, but it can take several days.
There are a few cases where no thumbnail will appear at all which happens to sites that either use several redirects, do not follow standard web conventions or cause errors when displaying in certain browsers. The only way to get a thumbnail in those situations is to fix the website to be error free.
Both categories are displayed using a complex logic that takes several factors about your listing and your website into account. Depending how new your listing is, it can take quite some time to make it to the front of the list.
PRO listings are always included in both categories, and while their ranked heavier, they may not appear necessarily in the first results.
BASIC listings are excluded from being listed in either categories.
New Website
You recently changed websites or updated your website link in your account but do not have the required reciprocal link in place
Hidden Page
You may have placed the reciprocal link on a "hidden" page that is not directly accessible from your homepage. For example if you were to place the reciprocal link on a page called links.html but your homepage does not actually link to that page directly, it will not work.
Noindex/Nofollow meta tag
If you've placed the link on a page that has a nofollow meta tag, it will instruct any search engines visiting that page to not follow any of the links on the page and obviously that wouldn't work.
Framesets
For websites that utilize a frame set, the link must be in a frame displayed on the homepage and the frame must be hosted on the same domain as the homepage
External Sites
The reciprocal link must be placed on the same domain as your website. If placed on your blog, facebook or myspace page it will not be detected.
Javascript/Flash Navigation
The reciprocal link must be placed as a plain html link (as displayed in your account). If placed inside javascript or flash it will not be detected.