Line 54, Column 10: document type does not allow element "p" here; missing one of "object", "applet", "map", "iframe", "button", "ins", "del" start-tag
<h1><p>From the latest low weight, switch-mode, Power Amplifiers to full siz…✉
The mentioned element is not allowed to appear in the context in which you've placed it; the other mentioned elements are the only ones that are both allowed there and can contain the element mentioned. This might mean that you need a containing element, or possibly that you've forgotten to close a previous element.
One possible cause for this message is that you have attempted to put a block-level element (such as "<p>" or "<table>") inside an inline element (such as "<a>", "<span>", or "<font>").
The problem is you’ve got your <p>s inside an <h1>, which is not allowed.
<h1> is for the top-level heading, and is only allowed to contain text and ‘inline’ elements. It is not allowed to contain ‘block-level’ elements such as <p>, and it certainly should not be used for long blocks of text.
And … aargh! What’s with all that Flash? Using Flash to make one or two small pieces on the website may be a good thing to do. Using Flash to make the whole website really isn’t. In some mitigation, you have at least got some content available to people without Flash, but bizarrely it’s different from what you’re serving by Flash. When you’re serving content by different methods, you should always make sure that people get the same content, whichever method of access they use*. That’s important for equality of access, and it’s important for people using search engines to find your site - otherwise the search engines may pick up a phrase that is in your non-Flash content, they go to the site looking for that phrase, and it isn’t there …
The exception may be if you are purposefully producing a slimmed-down version for mobile use, where you might want to cut back on content.
You have some <p> tags inside an <h1></h1>. h1 is used for level one headings. It really shouldn’t contain paragraph elements. Correct me if I am wrong, but if you remove the h1 tags and use CSS for your styling, would that not eliminate the error messages?