| URL | Passed Validation In Karppinen Study Feb. 2002 | Passed Validation In Saarsoo Study Jun. 2006 |
| 24-7 Co.,Ltd. | | |
| A-SIT | | |
| ACORD Corporation | | |
| Alisys Software | | |
| AME Info FZ LLC | | Yes |
| Argo Interactive Ltd | | |
| ARTSTAFF CO., LTD. | | |
| Asemantics S.R.L. | | |
| Bartimeus - Accessibility | | Yes |
| Bhrigus Software (India) Private Limited | | |
| CSI-Piemonte | | Yes |
| CSIRO | | Yes |
| DAISY Consortium | | |
| The Department of Broadband, Communications and the Digital Economy (Australia) | | |
| Department of Information Technology, Government of India | | |
| Digital Harbor Incorporated | | |
| Dot Com Infoway | | |
| Dreamlab Technologies AG | | |
| Electronic Data Systems (EDS) | | Yes |
| ENISA (European Network and Information and Security Agency) | | |
| Fotosearch Stock Photography and Footage | | |
| Fundación CTIC (Centro Tecnológico para el Desarrollo en Asturias de las Tecnologías de la Información y la Comunicación) | | Yes |
| Gijón City Council | | |
| Grupointermark 96, S.L. | | Yes |
| Hitachi, Ltd. | | Yes |
| HOB GmbH & Co. KG | | |
| IBM Corporation | | |
| Image, Video and Multimedia Systems Lab (IVML-NTUA) | | Yes |
| IMG SRC, Inc. | | |
| Infopark AG | | Yes |
| Infoteria Corporation | | |
| Innodata Isogen, Inc. | | |
| INNOVIMAX | | |
| Internet Academy, Inc. | | |
| Internet Association Japan (IA Japan) | | |
| Internet Content Rating Association | | Yes |
| Joint Info. Systems Comm. of the UK Higher Ed. Funding Council (JISC) | Yes | Yes |
| Joost Technologies BV | | |
| Lawrence Berkeley National Laboratory | | |
| Marden Edwards Limited | | |
| Mitsue-Links Co., Ltd. | | Yes |
| Mozilla Foundation | | Yes |
| National Research Council Canada | | Yes |
| New Zealand State Services Commission | | |
| NexTag, Inc. | | |
| Nextstage Corporation | | |
| NIC.br - Brazilian Network Information Center | | |
| Nominet | | |
| The Open University | | Yes |
| Opera Software | Yes | Yes |
| Origo Services Limited | | Yes |
| Oxford Brookes University | | |
| Page Traffic Web-Tech (P) Ltd. | | |
| Presidenza del Consiglio dei Ministri | | Yes |
| Progeny Systems | | Yes |
| Queensland University of Technology | | |
| Rensselaer Polytechnic Institute | | |
| REWERSE | | Yes |
| Rogue Wave Software | | |
| Royal National Institute for the Blind (RNIB) | Yes | |
| SBsquared Limited | | |
| Search Engine Optimization Inc. | | |
| Seresco, S.A. | | |
| SICS | | |
| SIZ Informatikzentrum der Sparkassenorganisation GmbH | | |
| Society for Technical Communication (STC) | | |
| Sogei (Societa Generale D'Informatica) | | Yes |
| STFC (Science & Technology Facilities Council) | | |
| Suchmaschinenoptimierung Sebcom | | |
| Symbian Limited | | |
| ThinkCo Ltd | | |
| Third Party Formations Limited t/a The Company Warehouse | | |
| University of Amsterdam | | |
| University of Bologna | | Yes |
| University of Bristol | | |
| University of Innsbruck | | Yes |
| University of Kent | | Yes |
| University of Manchester | | |
| University of Southampton | | |
| VeriSign, Inc. | | |
| Vision Australia | | Yes |
| Webexcel Solutions Limited | | |
| ZERO Factory, Inc. | | |