If users don't select importing starter.shoutwiki, the Main_Page created contains
```
<big>Welcome to your new site!</big><br/>
This is your new site! Feel free to start editing right away!
```
I'm unsure where the text originates, but I suspect the CreateWiki extension.
`<big>` has been removed from the HTML specification, so it's not even deprecated. It's gone. A functional, compatible option would be something like
```
<span style="font-size: larger;">Welcome to your new site!</span><br/>
This is your new site! Feel free to start editing right away!
```