Ambiguous reference to System.UI.Web.Extensions.dllhttp://blogs.msdn.com/juveriak/archive/2008/04/05/ambiguous-reference-to-system-ui-web-extensions-dll.aspxIf you install Visual studio 2008 while the 2005 version exists, and you have a website project that uses ajax, you're bound to run into the following issue: You'll see an error saying: "Ambiguous reference of System.UI.Web.Extensions.dll found" . Anden-USCommunityServer 2.1 SP1 (Build: 61025.2)Web Design &raquo; Ambiguous reference to System.UI.Web.Extensions.dllhttp://blogs.msdn.com/juveriak/archive/2008/04/05/ambiguous-reference-to-system-ui-web-extensions-dll.aspx#8361782Sun, 06 Apr 2008 02:43:31 GMT91d46819-8472-40ad-a661-2c78acb4018c:8361782Web Design &raquo; Ambiguous reference to System.UI.Web.Extensions.dll<p>PingBack from <a rel="nofollow" target="_new" href="http://web-design.crazyblogz.info/?p=2398">http://web-design.crazyblogz.info/?p=2398</a></p> re: Ambiguous reference to System.UI.Web.Extensions.dllhttp://blogs.msdn.com/juveriak/archive/2008/04/05/ambiguous-reference-to-system-ui-web-extensions-dll.aspx#8528089Wed, 21 May 2008 16:33:58 GMT91d46819-8472-40ad-a661-2c78acb4018c:8528089Ivan<p>I decided to move forward to 3.5 </p> <p>(Why use an old version?)</p> <p>I also found that I had to remove the old 1.0 assemblies from the GAC. &nbsp;HTH anyone that comes across this blog post.</p>