A common complaint about SharePoint was the lack of security trimming in the URL. Several solutions were proposed by the community which involved client side scripting or ISAP filters. The next version of SharePoint has a SPSecurityTrimmedControl that can be wrapped around almost anything it seems.
E.g.
<Sharepoint:SPSecurityTrimmedControl runat="server" PermissionsString="ManageWeb">
This should be hidden from everyone except the site manager<br>
</SharePoint:SPSecurityTrimmedControl>
The PermissionsString can contain a comma delimited list of permissions from the following (unconfirmed and possibly incomplete) list
OpenWeb
EnumeratePermissions
ManagePermissions
ViewUsageData
CreatePersonalGroups
CreateSscSite
BrowseDirectories
ThemeWeb
LinkStyleSheet
UseRemoteAPIs
UseClientIntegration
EditMyUserInfo
BrowseUserInfo
BreakCheckout
ViewPages
ViewFormPages
WriteWebPages
ManageSubwebs
ManageWeb
ManagePersonalViews
AddDelPrivateWebParts
UpdatePersonalWebParts
ManageLists
ViewListItem
ViewListItems
OpenItems
InsertListItems
EditListItems
DeleteListItems
ApproveItems
ViewVersions
DeleteVersions
CreateAlerts
ManageAlerts