[SalesForce] Use standard layouts in visualforce edit pages

My guess is that your VF page which you have done for accounts doesnt have a standardcontroller="Account" and your Vf page for contact has standardcontroller="contact"

If you want your VF pages to be available on your pagelayout then you need to define the standardcontroller as that object which you want the page to be embeded in.

yes it is.

go to Case --> buttons, link, Actions then find the Label "edit" and select the action edit. .. then you can override the std page with that vf one.

Now, say if you want to choose between a std page and the vf page? What you'd do is create a routing VF page. So, when the user clicks edit, he goes to the router. based on what ever criteria (i.e. ecternal user / internal user), he'll get sent to where he needs to go.

Example

if you need any paramaters from your previous page, you can get those via a referring page. you can make this call in your constructor to build your retURL for a cancel action, or if you need the referrinf record in any way

 //vf page
apex:page action={!router}>

 // in  controller

public pagerefernce getRouter()
    PageReference p ;   
    if ($UserInfo.getProfileId == '') <-- external profile{
        p = new PageReference(/apex/YourVFPage);
        }else{
        p = new PageReference('/'+this.case.id+ '/e?nooveride=1'
        }
    return p;
}