HotDog uses several syntax files to validate any code you create. These syntax files are separated by versions and browser support. For example, if you want to use only tags that are HTML version 3.2 compliant, you can specify that only allow HTML 3.2 tags are considered valid. This means that any tags or attributes that don't form part of this specification will be underlined.
This is particularly useful if you want to design your pages so that they are compatible with different browsers. (The HTML Property Sheet also displays the properties of each tag, making it very simple for you to ensure browser compatibility whilst editing - you just need to place your cursor within the tag in your editor window that you're interested in. By avoiding browser specific tags you can be fairly sure that your page will show up on many different browsers.)
Your Syntax Filter preferences let you control the syntax that is recognized by HotDog. To edit these:
In the Edit menu, choose Preferences and then navigate to Syntax Filters.
Using the Language drop-down list, select the language for which you wish to define the filter rule.
Using the Filter Rule drop-down list select the syntax specification you wish to use.
Click OK.