[MUSIC] >> Hi, and welcome to the lesson. Last time we talked a bit about how to load our HTML files to the Internet. And we also looked at some of the things that can happen that can go wrong when we're uploading files and how we might go about fixing them. That segues into this lesson which is about testing our HTML and exactly how we should approach it. For some reason, when people are learning programming, they sometimes get in the habit of making small changes to their files or their programs before they test them. And this can end up being a very frustrating experience. Let me demonstrate. So here we have a file from a previous lesson where we talked about how to put our data into an HTML table. I'm going to make sure this file is saved. I'm going to find that file on my file system. It's called html4.html and we'll look at it. And it has days one through five, it has an activity, and it has a number of minutes. So, let's say I want to change this. And I would like to add some more rows of data. Well, I may already be comfortable with this idea of an HTML table, so I'm just going to copy this data and put it here. And I'll save it and have a look. And it looks okay but then I realize that the last row is just a copy of the first row, so what I'll try now is going back. And I'll change this. I'd like this to be a 6, and so I'll make this a 6. And notice what I've done here. I've made a mistake and I did it on purpose to make a point. On line 35 I actually backspaced over a part of the closing tag for the table data. I'm going to save this because we'll just pretend that I don't know why I did this, and then we'll go back to the page. And we'll refresh, and notice here, this looks wrong. So, I found it right away, which is important, so we can go and fix it right away. The longer we leave the problem, the more likely it is that it'll be hard for us to fix. So I'm going to go back and look around and possibly notice what I've done here. As you practice, you'll see these things more quickly. And I'll backspace over that as well, and I'll save it, then we'll have another look, and this time it looks okay, but let's say instead that I did what I was talking about a moment ago and just sort of forgot to do some testing. So I've got my day, 6 here or maybe this is going to be Day 7, and let's say I also scroll up, I'm looking around at my HTML and I notice that I've got some white space here. And this amount of white space is fine, it works, but maybe you'd like it to be a little less white space. So, you close the white space there on line 15, and so these are closer together. Now notice what I've done here. I've made another typo. I have accidentally backspaced over the E in table. If I don't notice, and I save it, go and refresh, and now look at what I have. My output here, my HTML in my browser is drastically different than it was before, and because my first change was down at the bottom, I might be inclined to think that this is where the mistake was. And that would be a good guess except that I also made changes at the top. So, what I want to encourage you to do is test as you go. With each change try saving and testing. Now, this strategy can't work every time. Sometimes we do need to make multiple changes and testing this one change at a time isn't practical, but do try. And do try to keep your number of changes small before you test each time. Try to get into a habit of a change test, change test sort of mantra. And always test after you've made a relatively small number of changes. Now, as your skills grow you can stretch out a little bit and test a little less frequently but you should never go many minutes or even hours before testing. It will not get any easier to fix the problem if you wait to fix it until later. So keep these ideas in mind. Test as you go and next time, we'll be talking about adding style to our HTML so we can customize the HTML and have it look exactly like we want.