Hi,

in case of corporate site ASPX you can find the requested code in follwing two files:

1. ~/CMSTemplates/CorporateSiteAspx/Root.master
You can see that ID of control containing logo is imgLogo.

 <!-- Logo -->
        <div class="zoneLogo">
            <asp:HyperLink ID="lnkHome" runat="server" EnableViewState="false">
                <asp:Image ID="imgLogo" runat="server" AlternateText="Logo" BorderWidth="0" EnableViewState="false" />
            </asp:HyperLink>
        </div>

2. ~/CMSTemplates/CorporateSiteAspx/Root.master.cs
In the code behind is set path to the logo image. You can change the path in following method.

 protected override void OnPreRender(EventArgs e)
    {
        base.OnPreRender(e);

        ltlTags.Text = HeaderTags;
        lnkHome.NavigateUrl = ResolveUrl("~/Home.aspx");
        imgLogo.ImageUrl = ResolveUrl("~/Images-(1)/CompanyLogo.aspx");

        lnkCMSDesk.NavigateUrl = ResolveUrl("~/CMSPages/logon.aspx?ReturnUrl=~/cmsdesk/default.aspx&username=administrator");
        lnkSiteManager.NavigateUrl = ResolveUrl("~/CMSPages/logon.aspx?ReturnUrl=~/cmssitemanager/default.aspx&username=administrator");

        lnkSiteMap.NavigateUrl = ResolveUrl("~/SpecialPages/Sitemap.aspx");
        lnkDisclaimer.NavigateUrl = ResolveUrl("~/SpecialPages/Disclaimer.aspx");

        imgPowered.ImageUrl = UIHelper.GetImageUrl(Page, "Powered_by_kentico.gif");

        SignOutButton.ContentBefore = "<div class=\"signOut\">";
        SignOutButton.ContentAfter = "</div>";
    }

Best regards,
Ivana Tomanickova