function getObjectCss() {
	 var css = null;
	 try {
		css = document.styleSheets[0];
		if (!css) {
		   var head = document.getElementsByTagName("head").item(0);
		   head.appendChild(document.createElement("style"));
		   css = document.styleSheets[0];
		}
	 } catch (ex) {
		css = document.createStyleSheet("styles.css");
	 }
	 return css;
  }

  function changeCssRule(css, selector, rule) {
	if (css.insertRule) { // ff
		css.insertRule(""+selector+" { "+rule+" }", css.cssRules.length);
	} else if(css.addRule) { // ie
		css.addRule(selector, rule);
	}
  }

  function hide_box() {
	 var css = getObjectCss();
	 changeCssRule(css, "#login_content", "display: none;");
	 changeCssRule(css, ".show_hide_content", "display: none;");
  }