you need to "rel" tag in link.
<a href="/user" rel="lightframe[|width:400px; height:300px; scrolling: auto;]">My Account</a>
If you want show a specific region then use this.
<a href="/node/xxx #content-inner > *" rel="lightmodal[|width:700px;height:300px;]">Click to see only the content inside #content-inner</a>