The lawsuit, filed Nov. 12 in a Virginia court, alleges L90's adMonitor advertisement serving and tracking technology is too close to its own Dart system, according to a Wall Street Journal report. DoubleClick patented the Dart technology in September.

L90 plans to fight the case, claiming that the patent is too broad, but would not comment in detail due to the company's pre-IPO quiet period, the report said.

The company filed for an IPO in September, and plans to offer 10-12 million shares in its upcoming listing on the Nasdaq. No comment has been made on how the lawsuit could effect the IPO.

L90 last month unveiled with an upgraded version of its adMonitor.

If the patent is upheld to the broad limits which L90 suggests, it could have quite an impact on the online ad market if DoubleClick (DCLK) chooses to pursue similar infringement allegations to other rivals, said the report.