The practical value of WebRank as a measure of success is often discussed in SEO communities and the general opinion is that this is not the most relevant metrics. However, one of the benefits of WebRank is that it alerts Yahoo! Slurp that a new page has appeared, thus inviting it to spider it, if it is not already in the Yahoo! Search index.
When Yahoo! toolbar was launched in 2004, it had an icon that showed the WebRank of the page that is currently open in the browser. Later this feature has been removed but still there are tools on the Web that allow to check the WebRank of a particular page. For instance, this tool allows to check the WebRanks of a whole bunch of pages at a time.