You can use Sharepoint Client Object Model for this. Here is how to do it on the current web:
function CheckPermissionOnWeb()
{
context = new SP.ClientContext.get_current();
web = context.get_web();
this._currentUser = web.get_currentUser();
context.load(this._currentUser);
context.load(web,'EffectiveBasePermissions');
context.executeQueryAsync(Function.createDelegate(this, this.onSuccessMethod), Function.createDelegate(this, this.onFailureMethod));
}
function onSuccessMethod(sender, args)
{
if (web.get_effectiveBasePermissions().has(SP.PermissionKind.editListItems))
{
//User Has Edit Permissions
alert('YEAH, edit list permissions!');
}
}
}
from http://spdailytips.blogspot.se/2011/09/check-current-user-permission.html
Here you can find all the possible values for the Enum SP.PermissionKind.
This pattern will work on a List or a ListItem as well (like a page). Just make sure to load the object with context.load(theItem, 'EffectiveBasePermissions');
So in youyour case manageWeb
should do itgreat!