Okay the first thing I see wrong here is that is an old router.
Wireless G is pretty crummy. It means your maximum wireless internet speed will be 54Mbps, which converted to file byte transfer rate is actually 6.75MBps (bits versus bytes).
That might seem fast, but it's wishful thinking. There are a lot of factors that can get in the way of that speed. A lot of the time the router just has crummy hardware in it that doesn't have the processing power to give you the speed you are supposed to get. On my old Wireless G router I typically saw speeds closer to 1MBps, and that is pretty common if you look at the average benchmarks for Wireless G routers.
Solution: You need a new router. Go for one with Wireless N, your new Macbook should have it if it is less than 3 years old. A lot of the Wireless N ones also broadcast in G as well so you won't have to upgrade networks cards on older computers, you just won't get the fast speed of Wireless N on the older ones that don't have wireless NICs that support it.
Most of this stuff sounds like Theme customization. It's done using a combination of CSS, PHP, and HTML.
There's more information on it in the official WordPress Codex: http://codex.wordpress.org/Theme_Development
As far as moving the header image from a single page, that is only possible by setting up individual page templates: http://codex.wordpress.org/Stepping_Into_Templates
If you want to really learn how all of this works, download some free Premium themes from a professional theme designer and check out their templates' code. I think probably the best ones are available for download here: http://www.woothemes.com/product-category/themes/free-themes/
Good question jshepp!
There's a few things to consider that could be causing lag (latency and/or packetloss) on your network.
The first thing I always look at is the Internet Service Provider (ISP) speed. Are you on Comcast or Verizon? Or do you have DSL / Satellite / Radio internet? Whichever company is providing you internet service should have you signed up for a specific speed. GD wrote a really informative article regarding testing your internet connection speed here: http://www.groovypost.com/howto/geek-stuff/understand-your-interent-connection-test-its-speed/. Make sure before doing a speed test that everything that could possibly use internet is shut down. Are you getting the advertised speed that your internet service provider claims to be giving you? It probably won't be as high as they say, but it should be at least close.
Once you know the speed you are supposed to be getting, you need to consider how much bandwidth is being used. Netflix for example, uses about 900 MB of data per hour of viewing, assuming you don't pause it and keep watching continuously. 900 MB of data per hour = a data transfer rate of 256 KB per second. Or in Internet Service Provider lingo, that's 2 Megabits used per second. So if your Internet Provider tells you that you have a 3 Megabit connection, this means that you're going to lag no matter what when someone is watching Netflix because it is using up the majority of your maximum connection speed.Note most DSL companies don't offer more than 5 Megabits, and satellite almost never does.
If you have a fast connection with your ISP, like anything over 20 Megabits, then you shouldn't be running into Netflix lag because of that. In this case it is indeed your router. If you believe this is the reason, it's likely because you have a cheap router that isn't capable of handling large traffic between multiple computers on your local network. In this case, you can try updating the firmware, or installing custom open-source firmware like DDWRT (which I highly recommend). But even then, if the router is too cheap it won't fix your problems. For example I had this issue with a router slowing down when I would transfer large files from one computer to the other over the wireless network. It completely locked up because it just couldn't handle such a large amount of traffic all at once. I updated the firmware, installed custom firmware, hacked it, tweaked it. It improved a little, but it still locked up in the end whenever I tried to transfer large files. To solve my problem, I had to just buy a new higher-quality router.
I doubt it is this, but the last possible thing that could be causing a problem is a weak wireless signal. How strong does your computer show your signal to be? If you switch to a wired physical cable connection does it improve any?
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