Nice program Rated 4 out of 5 stars
With a bit of knowledge and judgement, WOT can help warn you about potentially dangerous web sites. I have used it for years. It can be annoying when a page I use is rated 'red' (unsafe), but has never affected my computer speed and can be customized to reduce intrusiveness. Web pages can be whitelisted.
WOT shows you what WOT members think of the safety of a web page. This add-on gets ratings from WOT members and shows them to you. You can add your ratings. The more people add ratings, the more accurate the ratings are likely to be. Since there are almost 2,000,000 using this Firefox add-on, the ratings can be helpful.
There are a couple of things to be careful about. Some companies and organizations add ratings to falsely skew the WOT outcome, so a safe site may come up as rated unsafe. Also, even 1,000,000 people may not know about privacy safety, so an unsafe site may come up as safe.
WOT is not designed to identify malware. I would suggest the NoScript, AdAware and Ghostery add-ons for safety, along with a virus protection software like Avast.