The ad firm says it chose Rackspace for its "robust infrastructure, scalable storage offering and ability to deliver IT service solutions". Adknowledge's Taglines product inserts behaviourally targeted logos and text links to user generated emails, newsletters and news alerts. Cubics, is the company's social advertising channel, serves targeted ad inventory across hundreds of social media applications.

Rackspace continues to grow at a rapid rate, and is currently experiencing a growth of 80 percent, says the company. Last year, Rackspace won Advanced Infrastructure Solutions, Hosting Solutions Partner of the Year, at the annual Microsoft Certified Partner Awards 2007.

The Web host also announced two high-level appointments - Florian Schiebl as European business director and Tarquin Bellinger as sales director - to help strengthen its European operations. Schiebl joins Rackspace from iPass where he served as managing director, overseeing the Central and Eastern European regions. Bellinger joins Rackspace from BT, where he led the company's 21st century network business development program.

"These are very exciting times for us as reaching the 4000th customer is an accolade we are very proud of," says Doug Loewe, managing director of Rackspace EMEA. "I feel confident that our belief in delivering Fanatical Support for our customers will continue to lead to success. While it's far easier to focus on technology, exceeding customer expectation is the real challenge, which is why we are absolutely committed to customer service. We are delighted to have Adknowledge as one of our customers and look forward to a fruitful relationship with them."

Last month, the company introduced Windows Server 2008 Standard, Enterprise and Web editions in conjunction with Microsoft's worldwide launch.