P.J.,
One of the spammers keep entering a spamming URL (using some variants each time) into the name or location field in the comments to my posts: sometimes with or without the “www.”, sometimes with or without “http”, and sometimes with or without a backslash.
URLs or URL fragments can be placed here, with each entry on a separate line. For instance, you could specify http://www.spam-king.com and EE would match any incoming URLs from that domain to block. Likewise, you could specify simply the word spam and EE would match any URL that contained that word, whether it was “www.spam-king.com” or “www.i-eat-spam.com”.
For example, if the URL I want to block is www [dot] spammer [dot] com, can I enter spammer [dot].com into the URL field in the blacklist module to block any comment when this URL is entered into the name or location field?
It doesnt’ need to be the name or comment field like I said it just has to be posted through EE. It can be any field
Also, what will the spammers see when this is triggered? Do they see a message page with a system message?
Yes exactly
I clicked on the button to allow the blacklist module to edit the htaccess file. Will this change what the spammers see?
Writing to a htaccess file means spammers are blocked from seeing your site completely
EE Docs : Blacklist/Whitelist Module