Thanks again Dom. Here is my map in total. Perhaps you can see what's up. The hyperlink is in the MonitoringSitesLayer. <esri:Map x:Name="MyMap" Extent="748437,575771,1204687,267438" Margin="10,20,20,20" IsLogoVisible="False" >
<esri:Map.Layers>
<esri:FeatureLayer ID="PimaCounty"
Url="http://gismaps.pagnet.org/ArcGIS/rest/services/AirQuality/MapServer/8" />
<esri:ArcGISDynamicMapServiceLayer ID="PAGBaseMap"
Url="http://gismaps.pagnet.org/ArcGIS/rest/services/StreetsBaseMap/MapServer"
VisibleLayers="0,1" />
<esri:FeatureLayer ID="AjoSO2Layer"
Url="http://gismaps.pagnet.org/ArcGIS/rest/services/AirQuality/MapServer/4"
OutFields="NAME, DESC"
Visible="false">
<esri:FeatureLayer.MapTip>
<Border Style="{StaticResource MapTip_Border}" >
<StackPanel Margin="7" Orientation="Vertical">
<TextBlock Text="{Binding [Name]}" Foreground="Black" FontWeight="Bold"/>
<TextBlock Text="{Binding [Desc]}" Foreground="Black" TextWrapping="Wrap" Width="400"/>
</StackPanel>
</Border>
</esri:FeatureLayer.MapTip>
</esri:FeatureLayer>
<esri:FeatureLayer ID="AjoPM10Layer"
Url="http://gismaps.pagnet.org/ArcGIS/rest/services/AirQuality/MapServer/3"
OutFields="NAME, DESC"
Visible="false">
<esri:FeatureLayer.MapTip>
<Border Style="{StaticResource MapTip_Border}" >
<StackPanel Margin="7" Orientation="Vertical">
<TextBlock Text="{Binding [Name]}" Foreground="Black" FontWeight="Bold"/>
<TextBlock Text="{Binding [Desc]}" Foreground="Black" TextWrapping="Wrap" Width="400"/>
</StackPanel>
</Border>
</esri:FeatureLayer.MapTip>
</esri:FeatureLayer>
<esri:FeatureLayer ID="AirPlanningLayer"
Url="http://gismaps.pagnet.org/ArcGIS/rest/services/AirQuality/MapServer/7"
OutFields="NAME, DESC"
Visible="true" >
<esri:FeatureLayer.MapTip>
<Border Style="{StaticResource MapTip_Border}" >
<StackPanel Margin="7" Orientation="Vertical">
<TextBlock Text="{Binding [Name]}" Foreground="Black" FontWeight="Bold"/>
<TextBlock Text="{Binding [Desc]}" Foreground="Black" TextWrapping="Wrap" Width="400"/>
</StackPanel>
</Border>
</esri:FeatureLayer.MapTip>
</esri:FeatureLayer>
<esri:FeatureLayer ID="TucsonCOMaintLayer"
Url="http://gismaps.pagnet.org/ArcGIS/rest/services/AirQuality/MapServer/5"
OutFields="Name, Desc"
Visible="false">
<esri:FeatureLayer.MapTip>
<Border Style="{StaticResource MapTip_Border}" >
<StackPanel Margin="7" Orientation="Vertical">
<TextBlock Text="{Binding [Name]}" Foreground="Black" FontWeight="Bold"/>
<TextBlock Text="{Binding [Desc]}" Foreground="Black" TextWrapping="Wrap" Width="400"/>
</StackPanel>
</Border>
</esri:FeatureLayer.MapTip>
</esri:FeatureLayer>
<esri:FeatureLayer ID="RillitoPM10Layer"
Url="http://gismaps.pagnet.org/ArcGIS/rest/services/AirQuality/MapServer/6"
OutFields="Name, Desc"
Visible="false">
<esri:FeatureLayer.MapTip>
<Border Style="{StaticResource MapTip_Border}" >
<StackPanel Margin="7" Orientation="Vertical">
<TextBlock Text="{Binding [Name]}" Foreground="Black" FontWeight="Bold"/>
<TextBlock Text="{Binding [Desc]}" Foreground="Black" TextWrapping="Wrap" Width="400"/>
</StackPanel>
</Border>
</esri:FeatureLayer.MapTip>
</esri:FeatureLayer>
<esri:FeatureLayer ID="SchoolsLayer"
Url="http://gismaps.pagnet.org/ArcGIS/rest/services/AirQuality/MapServer/2"
OutFields="SCHNAME, ADDRESS"
Visible="false">
<esri:FeatureLayer.MapTip>
<Border Style="{StaticResource MapTip_Border}" >
<StackPanel Margin="7" Orientation="Vertical">
<TextBlock Text="{Binding [SCHNAME]}" Foreground="Black" FontWeight="Bold"/>
<TextBlock Text="{Binding [ADDRESS]}" Foreground="Black" />
</StackPanel>
</Border>
</esri:FeatureLayer.MapTip>
</esri:FeatureLayer>
<esri:FeatureLayer ID="HospitalsLayer"
Url="http://gismaps.pagnet.org/ArcGIS/rest/services/AirQuality/MapServer/1"
OutFields="NAME, ADDRESS"
Visible="False" >
<esri:FeatureLayer.MapTip>
<Border Style="{StaticResource MapTip_Border}" >
<StackPanel Margin="7" Orientation="Vertical">
<TextBlock Text="{Binding [NAME]}" Foreground="Black" FontWeight="Bold"/>
<TextBlock Text="{Binding [ADDRESS]}" Foreground="Black" />
</StackPanel>
</Border>
</esri:FeatureLayer.MapTip>
</esri:FeatureLayer>
<esri:FeatureLayer ID="MonitoringSitesLayer"
Url="http://gismaps.pagnet.org/ArcGIS/rest/services/AirQuality/MapServer/0"
OutFields="*"
Visible="true" MouseLeftButtonUp="MonitorsFeatureLayer_MouseLeftButtonUp">
<esri:FeatureLayer.MapTip >
<Border Style="{StaticResource MapTip_Border}" esri:FeatureLayer.MapTipHideDelay="00:00:01.5">
<StackPanel Margin="7" Orientation="Vertical">
<TextBlock Text="{Binding [NAME]}" Foreground="Black" FontWeight="Bold"/>
<TextBlock Text="{Binding [ADDRESS]}" Foreground="Black" />
<TextBlock Text="__________________________________________" Foreground="Black" />
<TextBlock Text="Pollutants that are monitored at this site" Foreground="Black" />
<StackPanel Orientation="Horizontal">
<!--<TextBlock Text="PM10 - " Foreground="Black" />-->
<TextBlock Text="{Binding [PM1]}" Foreground="Black" />
</StackPanel>
<StackPanel Orientation="Horizontal">
<!--<TextBlock Text="PM2.5 - " Foreground="Black" />-->
<TextBlock Text="{Binding [PM2]}" Foreground="Black" />
</StackPanel>
<StackPanel Orientation="Horizontal">
<!--<TextBlock Text="CO - " Foreground="Black" />-->
<TextBlock Text="{Binding [CO]}" Foreground="Black" />
</StackPanel>
<StackPanel Orientation="Horizontal">
<!--<TextBlock Text="Ozone - " Foreground="Black" />-->
<TextBlock Text="{Binding [O3]}" Foreground="Black" />
</StackPanel>
<StackPanel Orientation="Horizontal">
<!--<TextBlock Text="SO2 - " Foreground="Black" />-->
<TextBlock Text="{Binding [SO2]}" Foreground="Black" />
</StackPanel>
<StackPanel Orientation="Horizontal">
<!--<TextBlock Text="NO2 - " Foreground="Black" />-->
<TextBlock Text="{Binding [NOX]}" Foreground="Black" />
</StackPanel>
<HyperlinkButton x:Name="myHyperLink" NavigateUri="{Binding [WebLink]}" TargetName="_blank" Content="Click here for more info." Foreground="DarkSlateBlue"/>
</StackPanel>
</Border>
</esri:FeatureLayer.MapTip>
</esri:FeatureLayer>
</esri:Map.Layers>
</esri:Map>