You can find this option on the "Ranking" tab within "Project | Website Options". This feature is an enhancement to the Search feature. Normally, when you search, you will see any search results listed on the right. In the example below, we have searched on the word "tutorial", without the use of the Ranking feature. There were two pages containing this word, as per the screenshot below:
We could have hundreds of pages of results, and the Ranking feature allows us to show the more relevant results at the top of the search results page. The Ranking tab looks like this:
When the "Enable Ranking" option is checked, then Ranking will be used when you next compile. The "Show Ranking Caption" option allows you to decide whether you want the ranking percentage displayed next to each result, with an optional caption. For example, you may want to rank the results but not show what the ranking percentages are.
The Ranking Caption is "Rank" by default, but you can leave this blank or set it to anything you like. Checking the "Use Percentage Symbol" will add "%" to the right of the numeric percentage result.
Below is a screenshot of how the results appear with the default ranking options checked:
You can see that The "Video Tutorials" page is ranked higher than the "11. Translating Images" page, but why? Well that is where the "Allocation of Percentage Values" comes in. There are three options, "Title", "Keywords" and "Help Text". In the example above, we are saying that if the "tutorial" search phrase is found in the "Title", allocate 15%, if it is one of the Keywords for that page, then allocate a further 25%, and it if appears in the Help Text then allocate a further 60%. In our results above, the "Video Tutorials" page, has the search phrase in the Title, Keywords and Help Text, so it gets 100%.
The "11. Translating Images" page does not have the search phrase in the Title or Keywords, but it does exist in the Help Text. The more times it exists in the Help Text the greater percentage of the 60% it gets. In this case it appears several times and gets rounded up to 61%.
You can assign your own weighting of values, for example, you may feel that if a search phrase appears in the Title then it should get 50%, etc. You can freely decide on how your users search results should be ranked, and it may be different for different websites.
Note: This feature is only available in the Corporate Edition.