Hi, I've been playing around with Inkscape over the past few days and so far I think it's absolutely awesome.
One query. Which fonts can safely be used when building a website.
I've designed stuff in this app and I am particularly interested in using the HP PSG font.
Is this part of the app, or is it coming from my Windows fonts folder?
Is this safe to use? or are there copyrights etc?

Welcome to InkscapeForum!

To my knowledge, Inkscape doesn't come with any fonts. As far as I understand, all the fonts listed when the Text tool is engaged, are the fonts installed on the computer. Inkscape can be picky about fonts. They must be well-built and entirely stable -- like the standard ones (Arial, Times New Roman, etc.). You might get non-standard fonts to work, but it's kind of a matter of luck. I've even had trouble with MS Sans Serif (converted to PDF). You'd think fonts named MS should be stable, but apparently not....or not enough for Inkscape's PDF conversion.

I know a very little bit about making websites, and as far as I understand, the main concern is what visitors to the website/page will see. If the font in the documents or images (that are uploaded to the site) are left as text, and the website visitor may or may not be able to see them. I think it depends on if the visitor actually has the font installed on their computer. If they don't, their computer will use some sort of default font. Some websites try to download the font to the viewer's computer, for viewing the webpage. But not all visitors' security will allow that to happen, and in that case, they get some default font.

To my understanding, the best way to make sure a font is diplayed as you want for all viewers, is to convert the text to path, before uploading the doc or image to the website. If the webpage is mostly text, this might not really be practical. But for something like a header/footer, banner, or perhaps the caption for an image or graphic, it should work well.

I don't know anything about the font you mentioned. I'm also on Windows, but don't have it. It might have been installed via word processor or some other program. And it would be on you to learn about any potential copyrights. An internet search would probably be helpful

Small update on HP PSG font...
http://typophile.com/node/27774

Any font can be used partially, just not as text but as image (raster or vector). By used I mean commercially. There are some more precise rules defining what is the difference between partial and complete, but since I`ve read about it some long time ago, can`t tell you where exactly you could find it. Now, I just follow my fontile senses in order to estimate if I am using some font partially or completely ,) Basically, you can use letters from any font, but font (aside of letters graphical appearance) also defines spacing, punctuations, and some more not so obvious graphical specifications, so if your usage of font may include those parts as well, then it is advisable to look out for the font license.

Perhaps, even more basically... vectorized letters could be used for logo design. If you sorted, reordered or made composition of shapes there should not be much difference between square and letter. On the other hand, if you used sw and font in it to write something... well, that`s what fonts are really for.

p.s.
If you want page viewers to see font(s) that you have chosen, you need to embed it (them). That way, font will be part of the page/site and appearance would not depend on viewers installed fonts.