Allow hyperlink on textarea

Question

I want to allow the insertion of a hiperlink (like www.google.cl) on a textarea that also can have text (similar to this page when creating a new question). The problem is that I don't know how to allow it, because sending the "a" TAG to the server (running asp.net), the server responds saying that the request is malicious. I was thinking about using encodeURIComponent, but I don't want to allow all HTML posibilites (for security reasons also).

Obviously when getting the information from the server and putting it on a "p" TAG, the hiperlink must work as a hiperlink.

What's the better approach?

Sending information written by the user to the server (example):

$.post({
    url: url,
    data: {
        content: encodeURIComponent($('#textarea_content').val())
    }
});

Getting information from server and showing it to the user (example):

$.get({
    url:url
}).done(function(data) { 
    $('#p_content').text(data);
}

NOTE: I don't want to deactivate post validation (validateRequest="false").