Hi Mark,
The reason it appeared to not be within the content is that mojoPortal adds a bunch of markup to the modules to give them the Artisteer borders, backgrounds, etc. To get this effect, try using the below code:
<div class="art-content-layout-row">
<asp:Panel ID="divLeft" runat="server" CssClass="art-layout-cell art-sidebar1 leftside" Visible="True" SkinID="pnlPlain">
<div class="art-block">
<div class="art-block-tl"></div>
<div class="art-block-tr"></div>
<div class="art-block-bl"></div>
<div class="art-block-br"></div>
<div class="art-block-tc"></div>
<div class="art-block-bc"></div>
<div class="art-block-cl"></div>
<div class="art-block-cr"></div>
<div class="art-block-cc"></div>
<div class="art-block-body">
<div class="art-Post-inner">
<div class="art-blockheader">
<div class="l"></div>
<div class="r"></div>
<div class="art-header-tag-icon">
<div class="t">
<h2 class=" moduletitle">Login Controls</h2>
</div>
</div>
</div>
<div class="art-blockcontent">
<div class="art-blockcontent-tl"></div>
<div class="art-blockcontent-tr"></div>
<div class="art-blockcontent-bl"></div>
<div class="art-blockcontent-br"></div>
<div class="art-blockcontent-tc"></div>
<div class="art-blockcontent-bc"></div>
<div class="art-blockcontent-cl"></div>
<div class="art-blockcontent-cr"></div>
<div class="art-blockcontent-cc"></div>
<div class="art-blockcontent-body">
<div class=" modulecontent">
<div id="membershiplinks" class="linkcontrols">
<portal:WelcomeMessage ID="WelcomeMessage" runat="server" RenderAsListItem="false" ListItemCss="firstnav" />
<portal:HomeLink ID="HomeLink" runat="server" RenderAsListItem="false" />
<portal:SiteMapLink ID="SiteMapLink2" runat="server" CssClass="sitelink" RenderAsListItem="false" />
<portal:MyPageLink ID="MyPageLink1" runat="server" RenderAsListItem="false" />
<portal:UserProfileLink ID="UserProfileLink" runat="server" RenderAsListItem="false" />
<portal:MailboxLink ID="MailboxLink1" runat="server" RenderAsListItem="false" />
<portal:MemberListLink ID="MemberListLink" runat="server" RenderAsListItem="false" />
<portal:RegisterLink ID="RegisterLink" runat="server" RenderAsListItem="false" />
<portal:LoginLink ID="LoginLink" runat="server" RenderAsListItem="false" />
<portal:LogoutLink ID="LogoutLink" runat="server" RenderAsListItem="false" />
</div>
</div>
<div class="modulefooter"></div>
</div>
<div class="cleared"></div>
</div>
<div class="cleared"></div>
</div>
</div>
<div class="cleared"></div>
</div>
<asp:ContentPlaceHolder ID="leftContent" runat="server"></asp:ContentPlaceHolder>
</asp:Panel>
</div>
As far as the button go, you will need to apply style to each individual link to hide the text but show a background image. I did this recently on this site: http://hyphensales.co.uk. Take a look at the Client Login button. There wasn't any text to hide in this case but you should be able to do this with some CSS trickery. Get the menu working and give the button a stab but I can help if you run into issues.
HTH,
Joe D.