I got this error while working with web app this is my master page
<head runat="server"> <link href="Styles/Site.css" rel="stylesheet" type="text/css" /> <asp:ContentPlaceHolder ID="head" runat="server"> </asp:ContentPlaceHolder> Error: The stylesheet http://localhost:55381/Login.aspx?ReturnUrl=%2fStyles%2fSite.css was not loaded because its MIME type, "text/html", is not "text/css". Source File: http://localhost:55381/Login.aspx Line: 0
Looks like your code is requiring a login to access the CSS stylesheet, and returning a HTML login page instead of the CSS.
To verify, try pasting the URL to the stylesheet into your browser, for instance http://localhost:55381/Styles/Site.css - if you get a login page instead of CSS, that's what you need to fix.
<location path="~/Styles"> <system.web> <authorization> <allow users="*"/> </authorization> </system.web> Where Styles is the folder that contains style sheet...i solved this way
@DavidPrecious gave a great answer that led me to the solution.
In my case, the local computer's Users group needed to be given Read permissions to the c:\Inetpub folder in order to allow the static content to be delivered properly.
Another possibility: you've modified your .htaccess file to serve css as html. Maybe something like this, for example:
<filesMatch "\.(htm|html|css|js)$"> ForceType 'text/html; charset=UTF-8' </filesMatch> (you would want to remove the "css" from the first line if you've done this.)
This is more likely an issue at your server side. you request style sheet page "Styles/Site.css" from the server of type "text/css", but your server might be responding to this request with "test/html". I had this issue when my server was running in python and my server was replying to requested css files with header text/html (as that of my index.html file). I re-arranged my server code and assigned the correct headers to its corresponding pages and my issue got resolved.