When ht://Dig performs a search, it does not search the text of each file within the search range; it queries the database of keywords generated when you last indexed your website. This index of keywords does not include html elements (<>) nor does it include the words specified in the bad words file (../htdig/common/badwords). You can index your website as often as you wish (although ht://D will automatically do it for you once a week).
Open the bad words file (../htdig/common/badwords) in your favorite text editor; add, revise, or delete the words that you want ht://Dig to skip when indexing your website.