Answer

Posting this here as 8 hours hasnt passed for me to answer my own question:

I figured this out. I removed Server.MapPath from the PreRender and it rendered it correct. Brain fart on my part. Thanks guys

in my code i have:

CssIncludes.Add("~/Sites/0/PageLayouts/Predefined/News/CSS/HeaderMenu.css");

Once rendered on page it comes out in the page source as:

 <link href='C:\inetpub\wwwroot\mysite\Sites\0\PageLayouts\Predefined\News\CSS\HeaderMenu.css' type='text/css' rel='stylesheet' />

now if i manually copy that css url and paste it in my browser, it loads the css fine, yet it will not show up on my c:\localhost\mysite\ at all!

Any solutions?

CSS Includes list:

public List<string> CssIncludes
    {
        get
        {
            if (_cssincluded == null)
                _cssincluded = new List<string>();
            return _cssincluded;
        }
    }

void Page_PreRender(object sender, EventArgs e)
    {
        foreach (string css in CssIncludes)
        {
            Page.Header.Controls.Add(new LiteralControl(string.Format("<link href='{0}' type='text/css' rel='stylesheet' />", Server.MapPath(css))));
        }
    }

remove ~ sign and try again, i hope it will work

Add website path key in web.config in appSettings section

<add key="Websitepath" value="http://www.yoursite.com" />

and make url like

includeCss(ConfigurationManager.AppSettings["Websitepath"].ToString()+"Sites/0/PageLayouts/Predefined/News/CSS/HeaderMenu.css";

more