Difference between spsite and spweb

spsite is site collection
spweb  are all sites under site collection

Excel graph look and feel issue- PowerPivot

Issue: 
Graph available in excel not looks fine while opening through web browser. Some of the Vertical line missed. The same graph works fine if it is opened with excel instead of web browser.
Resolution:
After a long research I found that the feature needs to be activate one feature at site collection and site feature:
I enabled once again the feature at "site feature" and "Site collection feature":
SharePoint Server Enterprise Site features
Features such as Visio Services, Access Services, and Excel Services Application, included in the SharePoint Server Enterprise License.
Please note: The excel graph view in web browser will be a problem for existing files but working for new files with same content.