[elitis]

seems to work fine if I add

document.getElementById('bld').addEventListener('click',iBold,false);

through the console. Could that mean the elements haven't loaded yet?
As for the dollar function, I added it as a means of shortening the code. Seemed redundant to keep typing out document.getElementById() when I could simplify it.

Updated code:
Javascript:

if (window.addEventListener){window.addEventListener('load',iFrameOn,false);}
else if (document.addEventListener) { 
	document.addEventListener('load',iFrameOn,false);
	$('bld').addEventListener('click',iBold,false);
	$('undrline').addEventListener('click',iUnderline,false);
	$('italic').addEventListener('click',iItalic,false);
	$('fontColor').addEventListener('click',iForeColor,false);
	$('unlist').addEventListener('click',iUnorderedList,false);
	$('orlist').addEventListener('click',iOrderedList,false);
	$('imge').addEventListener('click',iImage,false);
	$('deny').addEventListener('click',denyFR,false);
	$('accept').addEventListener('click',acceptFR,false);
	$('sbmt').addEventListener('click',sendData,false);
}
else if (document.attachEvent){document.attachEvent('onload',iFrameOn);}
else if (window.attachEvent){window.attachEvent('onload',iFrameOn);}

function $(element){return document.getElementById(element);}
function iFrameOn(){richTextField.document.designMode = 'On';}
function iBold(){richTextField.document.execCommand('bold',false,null);}
function iUnderline(){richTextField.document.execCommand('underline',false,null);}
function iItalic(){richTextField.document.execCommand('italic',false,null);}
function iForeColor() {
	var color = prompt('Enter a color', '');
	richTextField.document.execCommand('ForeColor',false,color);
}
function iUnorderedList() {
	richTextField.document.execCommand('InsertUnorderedList',false,'newUL');
}
function iOrderedList() {
	richTextField.document.execCommand('InsertOrderedList',false,'newOL');
}
function iImage() {
	var imgSrc = prompt('Enter image location', '');
	if (imgSrc != null) {
		richTextField.document.execCommand('insertimage',false,imgSrc);
	}
}
function denyFR() {
	var dfrHR = new XMLHttpRequest();
	var frURL = "fRequest.php";
	var denyRequest = 2;
	var statusOfRequest = "frStatus="+denyRequest;
	dfrHR.open("POST", frURL, true);
	dfrHR.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
	dfrHR.onreadystatechange = function() {
		if (dfrHR.readyState == 4 && dfrHR.status == 200) {
			$('fStatus').innerHTML = "Friend request denied";
		}
	}
	dfrHR.send(statusOfRequest); 
}
function acceptFR() {
	var afrHR = new XMLHttpRequest();
	var URL = "fRequest.php";
	var acceptRequest = 1;
	var aRequestStatus = "frStatus="+acceptRequest;
	afrHR.open("POST", URL, true);
	afrHR.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
	afrHR.onreadystatechange = function() {
		if (afrHR.readyState == 4 && afrHR.status == 200) {
			$('fStatus').innerHTML = "Friend request accepted";
		}
	}
	afrHR.send(aRequestStatus);
}
function sendData() {
	var hr = new XMLHttpRequest();
	var url = "rtf.php";
	var usrname = $('author').value;
	var txtField = window.frames['richTextField'].document.body.innerHTML;
	var vars = "author="+usrname+"&post="+txtField;
	hr.open("POST", url, true);
	hr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
	hr.onreadystatechange = function() {
	if (hr.readyState == 4 && hr.status == 200) {
		var return_data = hr.responseText;
		$('status').innerHTML = return_data;
	}
}
	hr.send(vars);
	$('status').innerHTML = "Posting...";
	}

HTML:

<iframe name="richTextField" id="richTextField"></iframe>
							<br />
							<div id="wysiwyg_bottom">
								<a id="bld" class="button" href="#">B</a>
								<a id="undrline" class="button" href="#">U</a>
								<a id="italic" class="button" href="#">I</a>
								<a id="fontColor" class="button" href="#">Color</a>
								<a id="unlist" class="button" href="#">UL</a>
								<a id="orlist" class="button" href="#">OL</a>
								<a id="imge" class="button" href="#">Image</a>
								<input id="sbmt" class="submit_button" type="button" name="submit" value="Post" />
							</div>
							<p id="status"></p>
						</form>