Do you mean the traffic to your sites is low? Or do you think there is something wrong with su.pr and your links? If you send us the URLs we can investigate.
StumbleUpon's recommendation engine is built on a complex algorithm that monitors a user's Stumble activity and connections to determine what users see while Stumbling. StumbleUpon does not disclose specifics about our recommendation engine, but you can see an overview of how it works here: http://www.stumbleupon.com/technology/.
That being said, we make no guarantees that content submitted via your personal account will gain, or maintain traffic - this is entirely in the gift of our members, whose 'likes' and ratings govern whether a site gains popularity and continues to circulate. Traffic is often not constant for a given site and, unless using Paid Discovery (our advertising platform), you can not necessarily expect a consistent source of traffic from StumbleUpon.
Please note that solely promoting your own content is not proper account behavior and that StumbleUpon users should only occasionally add their own content to StumbleUpon in order to avoid running into system restrictions. Ultimately though, StumbleUpon's Terms of Service prohibit use of user accounts to promote a specific website, product or service. In an effort to uphold the quality of sites within StumbleUpon, please also make sure your site does not violate any of our guidelines that could force us to ban it in the future: http://www.stumbleupon.com/help/repor...
If you wish to promote your content on StumbleUpon, you may do so with StumbleUpon Paid Discovery: http://paiddiscovery.com/. Paid Discovery accounts allow you to actively and legitimately promote a site to a targeted audience within our community.
If you have any other questions, please review our Terms of Service and Community Rules:
Please also read our blog article on how to properly use StumbleUpon to gain traction for your content: http://www.stumbleupon.com/sublog/how...