Index: src/ajax/ajax.js
===================================================================
--- src/ajax/ajax.js	(revision 208)
+++ src/ajax/ajax.js	(working copy)
@@ -5,7 +5,10 @@
 /**
  * Load HTML from a remote file and inject it into the DOM
  */
-jQuery.fn.load = function( url, params, callback ) {
+jQuery.fn.loadIfModified = function( url, params, callback ) {
+	jQuery.fn.load.apply(this, [url, params, callback, 1] );
+}
+jQuery.fn.load = function( url, params, callback, ifModified ) {
 	// I overwrote the event plugin's .load
 	// this won't happen again, I hope -John
 	if ( url && url.constructor == Function )
@@ -32,22 +35,30 @@
 	var self = this;
 	
 	// Request the remote document
-	jQuery.ajax( type, url, params,function(res){
+	jQuery.ajax( type, url, params,function(res, status){
+		
+		if( status == "notmodified" ) {
+			if( callback && callback.constructor == Function ) {
+				callback.apply( self, [res.responseText, status] );
+			}
+		} else if( status == "failure" && callback && callback.constructor == Function ) {
+			// callback only.
+			callback.apply( self, [res.responseText, status] );
+		} else {
+			// Inject the HTML into all the matched elements
+			self.html(res.responseText).each(function(){
+				// If a callback function was provided
+				if ( callback && callback.constructor == Function )
+					// Execute it within the context of the element
+					callback.apply( self, [res.responseText, status] );
+			});
 			
-		// Inject the HTML into all the matched elements
-		self.html(res.responseText).each(function(){
-			// If a callback function was provided
-			if ( callback && callback.constructor == Function )
-				// Execute it within the context of the element
-				callback.apply( self, [res.responseText] );
-		});
-		
-		// Execute all the scripts inside of the newly-injected HTML
-		$("script", self).each(function(){
-			eval( this.text || this.textContent || this.innerHTML || "");
-		});
-
-	});
+			// Execute all the scripts inside of the newly-injected HTML
+			$("script", self).each(function(){
+				eval( this.text || this.textContent || this.innerHTML || "");
+			});
+		}
+	}, ifModified);
 	
 	return this;
 };
@@ -78,8 +89,9 @@
 	/**
 	 * Load a remote page using a GET request
 	 */
-	get: function( url, data, callback, type ) {
+	get: function( url, data, callback, type, ifModified ) {
 		if ( data.constructor == Function ) {
+			type = callback;
 			callback = data;
 			data = null;
 		}
@@ -88,25 +100,36 @@
 			url += "?" + jQuery.param(data);
 		
 		// Build and start the HTTP Request
-		jQuery.ajax( "GET", url, null, function(r) {
-			if ( callback ) callback( jQuery.httpData(r,type) );
-		});
+		jQuery.ajax( "GET", url, null, function(r, status) {
+			if ( callback ) callback( jQuery.httpData(r,type), status );
+		}, ifModified);
 	},
+	getIfModified: function( url, data, callback, type ) {
+		jQuery.get(url, data, callback, type, 1);
+	},
 	
 	/**
 	 * Load a remote page using a POST request.
 	 */
 	post: function( url, data, callback, type ) {
 		// Build and start the HTTP Request
-		jQuery.ajax( "POST", url, jQuery.param(data), function(r) {
-			if ( callback ) callback( jQuery.httpData(r,type) );
+		jQuery.ajax( "POST", url, jQuery.param(data), function(r, status) {
+			if ( callback ) callback( jQuery.httpData(r,type), status );
 		});
 	},
 	
+	// timeout (ms)
+	timeout: 0,
+	ajaxTimeout: function(timeout) {
+		jQuery.timeout = timeout;
+	},
+	// Last-Modified header cache for next request
+	lastModified: {},
+	
 	/**
 	 * A common wrapper for making XMLHttpRequests
 	 */
-	ajax: function( type, url, data, ret ) {
+	ajax: function( type, url, data, ret, ifModified ) {
 		// If only a single argument was passed in,
 		// assume that it is a object of key/value pairs
 		if ( !url ) {
@@ -131,23 +154,46 @@
 		// Set the correct header, if data is being sent
 		if ( data )
 			xml.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
-	
+		
+		// Set the If-Modified-Since header, if ifModified mode.
+		if ( ifModified ) {
+			if ( jQuery.lastModified[url] ) {
+				xml.setRequestHeader("If-Modified-Since", jQuery.lastModified[url] );
+			} else {
+				xml.setRequestHeader("If-Modified-Since", "Thu, 01 Jan 1970 00:00:00 GMT" );
+			}
+		}
+		
 		// Set header so calling script knows that it's an XMLHttpRequest
 		xml.setRequestHeader("X-Requested-With", "XMLHttpRequest");
 	
 		// Make sure the browser sends the right content length
 		if ( xml.overrideMimeType )
 			xml.setRequestHeader("Connection", "close");
-	
+		
 		// Wait for a response to come back
-		xml.onreadystatechange = function(){
+		var onreadystatechange = function(istimeout){
 			// The transfer is complete and the data is available
-			if ( xml.readyState == 4 ) {
-				// Make sure that the request was successful
-				if ( jQuery.httpSuccess( xml ) ) {
+			if ( xml && (xml.readyState == 4 || istimeout) ) {
+				var statusstr;
+				if( jQuery.httpSuccess( xml ) ) {
+					statusstr = "success";
+					if ( ifModified && jQuery.httpNotModified( xml, url ) ) {
+						statusstr = "notmodified";
+					}
+				} else {
+					statusstr = "failure";
+				}
 				
+				// Make sure that the request was successful or notmodified
+				if ( statusstr != "failure" ) {
+					// Cache Last-Modified header, if ifModified mode.
+					if ( ifModified && xml.getResponseHeader("Last-Modified") ) {
+						jQuery.lastModified[url] = xml.getResponseHeader("Last-Modified");
+					}
+					
 					// If a local callback was specified, fire it
-					if ( success ) success( xml );
+					if ( success ) success( xml, statusstr );
 					
 					// Fire the global callback
 					jQuery.event.trigger( "ajaxSuccess" );
@@ -155,7 +201,7 @@
 				// Otherwise, the request was not successful
 				} else {
 					// If a local callback was specified, fire it
-					if ( error ) error( xml );
+					if ( error ) error( xml, statusstr );
 					
 					// Fire the global callback
 					jQuery.event.trigger( "ajaxError" );
@@ -169,14 +215,31 @@
 					jQuery.event.trigger( "ajaxStop" );
 	
 				// Process result
-				if ( ret ) ret(xml);
-
+				if ( ret ) ret(xml, statusstr);
+				
 				// Stop memory leaks
 				xml.onreadystatechange = function(){};
 				xml = null;
+				
 			}
 		};
-	
+		xml.onreadystatechange = onreadystatechange;
+		
+		// Timeout checker
+		if(jQuery.timeout > 0) {
+			setTimeout(function(){
+				if(xml) {
+					xml.abort();
+					// for Opera. Opera isn't call onreadystatechange when abort.
+					if(xml) {
+						onreadystatechange(1);
+					}
+					xml = null;
+				}
+			}, jQuery.timeout);
+		}
+		
+		
 		// Send the data
 		xml.send(data);
 	},
@@ -193,6 +256,22 @@
 		} catch(e){}
 		return false;
 	},
+	// Determines if an XMLHttpRequest returns NotModified
+	httpNotModified: function(xml, url) {
+		try {
+			
+			if( xml.status && ( xml.status == 304 ) ) {
+				return true;
+			}
+			// Firefox always returns 200. check Last-Modified date
+			if ( xml.getResponseHeader("Last-Modified") ) {
+				if( xml.getResponseHeader("Last-Modified") == jQuery.lastModified[url] ) {
+					return true;
+				}
+			}
+		} catch(e){}
+		return false;
+	},
 	
 	// Get the data out of an XMLHttpRequest.
 	// Return parsed XML if content-type header is "xml" and type is "xml" or omitted,