Need regex pattern for HTML Charcter validation using Javascript or Jquery

Hi friends,

I need to validate text box should not allow only html special characres(<,>).Please can you give me regular expression using jquery.I can enter any charcters except (<,>).If i enter these characters i am getting below error.
"A potentially dangerous Request.Form value was detected from the client (ctl00$ctl00$MainContent$uxHome$uxQuickSearch$txtKeyword="<test"). "
To avoid this error i want to validate text box not allowing html characters.
Please provide me regex pattern with jquery or Javascript.

Thanks
Sandhya