how do you delete or block others from seeing uyou online on a dashbaord

[ZIRX]

how do you delete a avatars dashboard

[Lindal Kidd]

I'm not sure what you mean...your "Dashboard" is the first page you see when you log on here to the Second Life website.  You can't delete it!  It gives you important information about your account.  Don't worry, no one else can see it (unless they've gotten access to your password, in which case you have more serious problems.)

Perhaps you mean a "HUD"?  A HUD is a "Heads Up Display", a set of controls that appears on your screen in the Second Life viewer.  HUDs are used for many things...to adjust Mesh bodies, to apply colors and textures to clothing or shoes or hair, to control nonhuman avatars, to operate your animation overrider (AO), and for anything else that needs special buttons or menus to control it.

To take off a HUD you don't need, simply right click it, right there on your screen, and select Detach.

[Amethyst Jetaime]

If you mean the https://my.secondlife.com page you can't block an individual person but you can change your settings so only friends can see the information.  Go to that page and then go to Settings and the Privacy Tab then change your's using the drop down boxes to the right of each section title to your choice of who can see it.  

Everyone means anyone searching the web, regardless whether they are a SL member or not, Second Life means only those with a Second Life account can see the information, and of course Friends means only people on your Friends List.

[Alwin Alcott]

it's all guessing... but do you perhaps mean hide your profile?...

the only thing you can do is uncheck show in search... but that won't really hide it, if they click you it will be shown.