Hi adnanali,

1- Drag and drop your viewer on the page .

2- The register tag will be generated at the top of the page .

3- Go to webconfig >> copy the version number from line similar to this tag.

<add assembly="CrystalDecisions.Web, Version=10.5.3700.0, Culture=neutral, PublicKeyToken=692fbea5521e1304"/>

4 - Paste the version number instead of the version on the register tag.

<%@ Register Assembly="CrystalDecisions.Web, Version=10.5.3700.0, Culture=neutral, PublicKeyToken=692fbea5521e1304" Namespace="CrystalDecisions.Web" TagPrefix="CR" %>