I fixed the problemand can post through WYSIWYG.
I needed to add: <httpRuntimerequestValidationMode="2.0"/> to my web.config file
I googled, “A potentially dangerous Request.Form value wasdetected from the client iis 7”, looking for something that might have changedin IIS 7.5 or .net4.
I found a posts indicatingsomething had changed between 3.5 and 4.0, people were getting thus under 4.0and not under 3.5 even when using the controlRenderingCompatibilityVersion="3.5"attribute in the pages tag of the web.config file.
This setof posts: https://stackoverflow.com/questions/2473972/a-potentially-dangerous-request-form-value-was-detected-but-validateinputfalseprovided
the solution and had a link to a Microsoft whitepaper https://www.asp.net/learn/whitepapers/aspnet4/breaking-changes#0.1__Toc256770147The
white paper describes changes that have been made for the .NET Frameworkversion 4 release that can potentially affect applications that were createdusing earlier releases, including the ASP.NET 4 Beta 1 and Beta 2 releases. The relevant section reads as follows: ASP.NET Request Validation
The request validation feature in ASP.NETprovides a certain level of default protection against cross-site scripting(XSS) attacks. In previous versions of ASP.NET, request validation was enabledby default. However, it applied only to ASP.NET pages (.aspx files and theirclass files) and only when those pages were executing.
In ASP.NET 4, by default, request validation isenabled for all requests, because it is enabled before the BeginRequestphase of an HTTP request. As a result, request validation applies to requestsfor all ASP.NET resources, not just .aspx page requests. This includes requestssuch as Web service calls and custom HTTP handlers. Request validation is alsoactive when custom HTTP modules are reading the contents of an HTTP request.
As a result, request validation errors mightnow occur for requests that previously did not trigger errors. To revert to thebehavior of the ASP.NET 2.0 request validation feature, add the followingsetting in the Web.config file:
<httpRuntime requestValidationMode="2.0" />
However, we recommend that you analyze anyrequest validation errors to determine whether existing handlers, modules, orother custom code accesses potentially unsafe HTTP inputs that could be XSSattack vectors.
I also realized Iposted in the InstantKB section, not the InstantForum section. Sorry for the error.