The red wavy line is your spell checker installed in your browser. Older slower machines have trouble when too many add ons and memory resident software is loaded.
Firefox add ons are easily added and removed if they are giving you problems.
IE explorer lets you decide what add ons, active x, and com components you want to run. Knock off the ones you don't need.
If you get the stuff out of the road that you don't need, you will see improvements in your computer and browser speed. Note that wireless connections are slower than hard wired. Check your old hardware (switches, hubs, routers), see if it is limited to 5 or 10 Mbps.
If you have one slow speed device in series in your home network between your ISP's modem and your computer, it is a bottleneck.
Latest versions of IE aren't handling the enter key correctly on this site (on PCs obviously). For each enter key stroke (carriage return) hold the alt key down and type the decimal code 013 on the keypad, then release the alt key. Or easier yet, switch to a different browser.
You need to do some hardware and software troubleshooting on your systems to see what the problem is, so you can decide where the problem is. When you find the trouble spot, then of course you will be able to fix it. And obviously this site is slow when overloaded, or when your ISP is overloaded, or throttling your throughput.
Tom