Is there a way in which a URL can be scanned before we open the page?
You can use this ,
I think this is what you are looking for.
Prachand MCSE-2012 Symantec Technical Specialist (SCTS)
You can use Symantec Web Security It is a combined content analysis solution for a company's Internet access, offering both automated virus scanning and content filtering at the Web gateway level. Because it operates at the Web gateway, it is able to protect all users throughout the organization who access Internet content (HTTP/FTP) through that gateway. According to information supplied by Symantec, their product "...supports all firewalls ... as well as proxy and caching servers."
The product is configured and managed via an HTML based interface, allowing administrators to setup and control the product from any Web browser. Content filtering is accomplished via a combination of list-based algorithms (i.e., administrators can select from among 31 pre-defined categories of Web sites containing Symantec's international URL filter list for blocking) and real-time, multilingual content analysis technology known as Dynamic Document Review allowing for the filtering of potentially objectionable Web sites that have not yet been categorized. Filters can be applied to both individual users and user groups and can also provide for scheduled access. Reports can be generated supplying both virus and content filtering information.
For virus scanning, Symantec Web Security employs Symantec's own NAVEX Scanning engine and Digital Immune System, which provide for the automatic submission and response for detected viral threats. The scanning engine, in particular, is designed such that it can be updated without requiring the Web gateway software itself to be shut down.
You can also try http://www.symantec.com/business/messagelabs-web-security