One of the features more important released in SharePoint 2010, is the possibility to host the “Office Web Apps” and open or edit document of Microsoft Office in the web. What I means with that is to have the possibility that the user could open or edit each document created by Microsoft Office client in the web through different browser. This capability works fine in Internet Explorer 7 or higher, but works fine in others browsers as Firefox, Safari, to have more information about the browser compatibility access here.
[Office Word Web] 
[Office Excel Web] 
[Office PowerPoint Web] 
[Office OneNote Web] 
The first thing that we will do is install the Office Web Apps component in all servers that were installed with SharePoint Server 2010. Once the Office Web Apps is installed, we must run the configuration Wizard of SharePoint 2010. When the wizard finished, the central administration will be open in the browser as we can see in image 1. There we are going to the “Managed Services Application” to review the new services created by Office Web Apps in our SharePoint, as we can see in image 2.
[Image 1] 
[Image 2] 
The services applications installed by Office Web Apps are ready to use by default but we could configure some of them as we want or we need. The next step is to associate the service or services of Office to our Web Application in SharePoint. To do that, we must enter to the option “Managed Web Applications”, as we can see in image 3.
[Image 3] 
In this section we have all web applications created in SharePoint 2010. We are going to select the application that we want add Office Web App and we are going to select the button “Service Connections” in the toolbar to open a new windows configuration as we can see in image 4 . This window shows the services applications associated with the web application and by default the configuration could be “Default”. We must change the option in the Drop Dow List control to “Custom” as see in image 4 and we are going to select the services that we want have associated to this web. Some of these services are of the Office Web Apps; I marked in red some of them as see in image 4.
[Image 4] 
In image 5 we can see what happens if we don’t have associated or configured “Office Web Apps” correctly in SharePoint 2010.
[Image 5] 
In the image 6 we can see a Word document opened in the Internet Explorer using “Office Web Apps” with a format, images, header and more thing of Microsoft Office client , excellent because the document don’t lost the format.
[Image 6] 
To open the documents in the browser we must have activated the feature “Office Web Apps” in the site collection feature of the web where we associated the application services, as we can see image 7.
[Image 7] 