using excerpt function breaks sidebar

I’m a newbie hacking my way through this.

Someone else created my website for me and integrated my blog into the website then turned it over to me to do anything else I wanted. So far so good. I’ve been able to do most things I want with the blog except to get the excerpt function working.

The theme is basic simplicity.

What I tried doing was editing the index file and replacing “content” with “excerpt” which worked fine to pull up the excerpts except that it made my sidebar disappear and the text overflowed to the far edge of the sidebar.

Here is the link to the site: http:www.susantaylorbrown/blog

Thank you for any thoughts on how to make it work and stay within the proper area.