HTML Code messed up

A few months ago I tried to add a tag to my blog to connect to another blog. I thought I knew what I was doing, despite not knowing much about HTML I had done this before without issue. Once I added it my whole website got messed up. After a few hours I got everything mostly back to normal, but there are some things that are still not right. The font is different, my polls stopped working, my shareholics isn’t working properly, all in all my site isn’t the same as it used to be. I am looking for someone who would be willing to look and give me advice, or if someone knows where I can look. I want to make sure i get good advice, I want to avoid being hacked etc. I just don’t know where to go next! Thanks for your help!

https://www.lookbetweenthelines.com