If you've ever received a comment that looked like an advertisement or a random link to an unrelated site, then you've encountered comment spam. Blogger has several built-in measures for dealing with comment spam and other associated dastardly behavior. Check them out:
1. Word Verification You can enable word verification for your comments. This will require an extra step in the commenting process, which will deter automated comment spamming systems, since it takes a human being to read the word and pass this step. Mostly, spam is automatically done by softwares which can't pass the word verification, so enabling this option is a good way to prevent many such unwanted comments. Blogger / Google word verification is tough, difficult to interpret sometimes, but still possible. However, when you login to your blogger account, you will bypass this step everytime you comment on your own blog. Location: Dashboard >> Settings >> Comments2. Comments Moderation You can enable comment moderation, which will let you view new comments and approve or reject them before they appear on your blog. Whenever you receive some comments, a link to moderate them will appear in your dashboard. Location: Dashboard >> Settings >> Comments3. Email Notification You can choose to receive notification by email when new comments have been posted on your blog. This way, you can monitor them for spam and delete them when necessary. This is useful when you don’t have the time to moderate all comments one by one, but still want to monitor them. Location: Dashboard >> Settings >> Comments4. HTML Restriction Only five html tags are accepted:<a> (for making links ) <strong> and <b> (for making text bold ) <em> and <i> (for making text italicicized ) Location: Secure Blogger Servers (Inaccessible by users)5. NoFollow Tag All links will automagically use the rel="nofollow" tag, so they'll receive no PageRank boost. However, this is sometimes considered not too effective in bulding healty atmosphere around blogs, therefore some bloggers remove it. If you want to disable it as well, use this . Location: Dashboard >> Layout >> Edit HTML >> Expand Template Widgets Source: Blogger Help, edited as necessary by Isaac Yassar