For a first time, it's looking alot better than most first-timers' websites do.
I've got a few comments:
I'll start with the coding. You've set your DOCTYPE to XHTML 1.0 Strict, yet you do not have what classifies as "strict" XHTML, or even valid XHTML at all. Stuff like <br> should be done <br />. Tags that don't have a closing tag should instead end with a /> rather than just a normal >. This applies to single tags such as <img />, <br />, <link /> (for style sheet linking). There are more. Visit the
www.w3schools.com xhtml section for exact details.
Goto
http://validator.w3.org/ to validate and check for yourself.
I would recommend setting your DOCTYPE to xhtml transitional. It still requires you to use proper XHTML, but it's not so **** strict
On the other hand, the CSS validates perfectly, so good work there
There also minor nitpicks like
padding:0px 0px 0px 0px;
Which can be simply done as
padding: 0;
Because when all values are equal, you only need one number. And when it's 0, you don't need to specify units. 0 is 0. That's just me being anal-retentive, though 
Also, try playing with different fonts other than Comic Sans. That's just my personal vendetta against Comic Sans coming through. I think there are better, more professional serif fonts to choose from.
Apart from that, the CSS looks alright. Maybe you could make sure the links underline or change colour when you hover over them? That just helps with recognizing them and stuff like that (for the dummies out there

)
Anyway, onto the visuals:
1. It might just be my eyes, or my monitor, but the red is just a little bit too bright for me... it is a little distracting, and makes my eyes sore after looking at the site long enough. You may want to maybe tone it down a few notches? Maybe more pastel, or darker... just a red that isn't so "rich" (or bright) so to speak.
2. I am, however, liking the textured background you're using for the main content background. Top job on that, it's good. Just maybe get the body font to "pop" out a little more against it (try playing with fonts like I said).
3. The header/logo could do with some overall refinement, I think I can almost see jpeg artifacts around the images of the girl/cat... may be me and my anal-retentiveness again >_< It suits the style of the page, but could look better. No specfic crits here, it's just not too interesting to look at.
4. Maybe change the black lines in the menu to be a little thinner... maybe try adding extra sides, to make them boxes, and the background colour of the boxes can change when hovering. Just an idea.
5. If you happen to get a professional style portrait photograph of your lovely nan, then put that up instead, it may help in conveying a sense of "professionalism". I'm not saying the current photo is a bad one, or the site is unprofessional, just that it could be better
These are all pretty small nitpicks which you can possibly try playing with, or not... but the site looks great either way, good work.
Conclusion: Nice simple design, for a simple site. Generally, the simpler you keep things, the less problems you are likely to encounter with stuff like cross-browser compatibility, text-only browsers etc etc.
Also, bonus points for a site map
