my a/c is working properly but on left corner of task bar show "error sign and done but error" why?

Well this could be anything from problems loading Java Scripts, ActiveX, programming error of the web page, browser imcompatibile. You might try to delete your temporary internet files and cookies, as well as updating your version of Java from www.java.com/download.

If it is the web pages problem, you can't solve it unless you are the webmaster or creator of the Web page. So in that case you have nothing to do.

Another reason is the web page you are viewing is not fully loaded. May be some part of it or part of the scripts the Web page is using. So in that case hit the Refresh button in your browser to load it. Sometimes it helps.