read text file and append with string.format?

Hi,
I have a text file which contains html content along with the css class in it with { }
And i have a link with <a  href="{0}">Here</a> in the text file.
I read the text file into string and try to append the string with string.Format but it shows error as the string was not in correct format.
string newcontent= string.Format(textfilecontent, url); if i remove the css class with { } then it works correctly.
Is it possible to ignore the css class with { } and format the string with above code?
Thank you.