If you are working in an enterprise environment chances are that you would be accessing this page behind a proxy. Your browser would have a proxy setting like hostname : abc.blah.blher.com and port would be something like 8080.
However if you are sitting behind the proxy and you need you tomcat server to access resources over the internet then these are the VM arguments that the launch configuration should have along with the standard list. Of course, you could also increase the heap size that you want to allocate to tomcat
and to increase the heap just mention -Xmx1024m
Now for using the proxy settings on Eclipse
Note that this is required to download any plug ins etc i.e. whenever Eclipse wants to access the internet or the HTTP resource outside your enterprise network
Goto Window -> Preferences ->General->Network connections and add the proxy settings there