Kontera Ads: The Single Underline Trick and In-Text Ads Today

Kontera ads were one of the best-known in-text advertising services of the 2000s, turning words inside blog posts into double-underlined ad links. In 2008 a code tweak spread across forums that made these ads show with a single underline, and we looked at whether publishers should use it. This updated article explains that trick, what happened to Kontera, and how in-text ads work today.

Quick answer: Kontera ads were in-text ads shown with a double underline so readers could tell them apart from normal links. A single-underline code made them blend in, but Kontera said it did not recommend or authorise the change. Kontera was bought by Amobee, the advertising unit of Singtel, in 2014. Today Google AdSense offers its own in-text links called Ad intents, which you can switch on or off.

What were Kontera ads?

Kontera ran an advertising platform that turned words in an article into links to ads. Unlike Google AdSense, which showed ads beside the content, Kontera’s ContentLinks appeared within the text itself. Hovering over a double-underlined word opened a small ad box, and publishers earned when readers clicked.

The single underline trick for Kontera ads

Kontera’s ads normally showed with double underlines. In 2008, many sites started showing them with single underlines, and the secret soon came out: several websites revealed that a line of Kontera code did the trick.

var dc_single_line = 'yes';

Single underlines blend in better if your site’s normal links are also underlined, which can raise click rates and earnings. But it confuses readers, who are led to ads instead of the links you suggested, and accidental clicks inflate what advertisers pay. Many regular readers already found in-text ads intrusive, and this kind of blending was not welcome.

What Kontera said

Although the code was pasted all over the web, I warned publishers to check with their Kontera account manager before using it, or risk a ban. I expected Kontera might allow it only on sites that removed underlines from normal links with CSS, where single-underlined ads would still stand out.

Update: Vered from Kontera then gave the official view: Kontera did not recommend single underlines for ContentLinks, because they confuse readers about what is an ad, and did not authorise making this change.

What happened to Kontera?

In June 2014, Amobee, the digital advertising unit of Singtel, bought Kontera for about $150 million, as part of a wider expansion of its ad business.

In-text ads in 2026

The idea of turning words into ad links has not gone away:

• Google AdSense Ad intents: AdSense can add in-text links, anchors and chips on your pages. See how to turn off AdSense shopping links and ad intents if you do not want them.
• Auto ads: AdSense Auto ads can place many formats for you. Our AdSense Auto ads guide covers the settings.
• Infolinks: a long-running ad network for publishers, focused on contextual ads.

Lessons from the Kontera underline debate

• Keep ads clearly different from your own links. Blending ads into content can break ad network policies.
• Never copy ad code tweaks from forums without checking the network’s rules.
• Think about readers first: intrusive ads can cost you more in lost visitors than they earn.

FAQ

Does Kontera still exist?

Kontera was acquired by Amobee in 2014. If you want in-text ads today, look at current options such as AdSense Ad intents rather than old Kontera code.

Why did Kontera use double underlines?

Double underlines made in-text ads look different from normal links, so readers could tell they were ads.

Was the single underline code allowed?

No. Kontera said it did not recommend single underlines for its ContentLinks and did not authorise the change.

Are in-text ads still used?

Yes. Google AdSense offers in-text links through Ad intents, and other networks offer contextual formats.