Problem:
Could not load file or assembly 'CrystalDecision.web, version=10.5.3700' on web page. I found the register tagprefix tag under the code behind of the aspx page has the following tag and figured it is a dll problem.
<% Register TagPrefix="cr" Namespace="CrystalDecisions.Web" Assembly="CrystalDecision.Web, Version=10.5.37... %>
Solution:
Navigate to SAP BusinessObjects url : http://wiki.sdn.sap.com/wiki/pages/viewpage.action?pageId=56787567
And download the crystal dlls version 10.5.37. Install the crystal GAC dlls on the web server.
Restart the IIS as the GAC is now refreshed with the latest crystal reports dll.