If zoom in/out tools were used on the map control, data is zoomed in/out when user right click on the map. This is not a desired behavior if a context menu is used in the web application, because map zooms in/out and then the context menu appears.
Override the _onClick function of MapBase by adding the following script block after the form close tag (</form>):<script type="text/javascript">ESRI.ADF.UI.MapBase.prototype._onClick = function(s,e){}</script> Normally you should be able to remove the event handler explicitly... but I was unable to do this. Likely because the delegate to the handler was created dynamically in MapBase initialize:this.add_click(Function.createDelegate(this, this._onClick));