My sidebar is at the bottom

Looks like a CSS formatting issue. When I am troubleshooting this stuff, I like to add a 1px solid color border on each div in the structure to see what one is causing the issue. I suspect that your main content div and sidebar divs are too wide for the area assigned so it’s kicking the floated element below.

check these divs:
#content
.hfeed
#tag_cloud-3
.page

*css structure issue

Also, check the div .aside

Have changed the px value of the .aside in my screen.css file but doesn’t seem to have had any effect.

Also done the same with the hfeed value

It did work at one time. Very frustrating.

I’m not able to add the 1px you suggest as I wouldn’t know where to start

The 1px trick is handled in the css file, either screen.css, or style.css. Also, sometimes content in a main content column will be wider than the specified width and you can hide the overflow to keep your css layouts from exploding.

Try two things for starters, troubleshoot the div widths by adding the border: 1px solid red; (or a different color for each div so you can tell them apart) and seeing if the overflow of the content can fix the layout issue.

so, add this to your existing css and use the border on other divs on the page, like #content.

.aside {border:1px solid black;}
.page {border:1px solid red; overflow:hidden;}