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Run Time Problems. My ASP.NET Web Forms ReportViewer looks messed up


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This article is related to the obsolete ASP.NET Web Forms Report Viewer. We strongly advice to Migrate to the HTML5 Viewer.


The obsolete ASP.NET Web Forms ReportViewer looks messed up - its styles and images are missing.


  1. Check if runat="server" is present in your web page's head tag.
  2. Check if the web report viewer's http handler is registered in the web.config file. If the app is deployed on IIS7 and setup to work in integrated mode, make sure preCondition attribute is present at the end of Telerik.ReportViewer handler:

        type="Telerik.ReportViewer.WebForms.HttpHandler, Telerik.ReportViewer.WebForms, Version=x.x.x.x, Culture=neutral, PublicKeyToken=a9d7983dfcc261be" 
        path="Telerik.ReportViewer.axd" verb="*" 
  3. Check if the report viewer's styles are registered on the page. This can be accomplished with http debugging proxy like Fiddler.
  4. Check for global styles defined in the application which affect the page with the report viewer and conflict with the report viewer's styles. Remove any style declarations from the page. Make sure the global style rules do not affect HTML elements directly, but are applied through the CssClass property.
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