Every conference I speak at I tend to get a site clinic, but it still surprises me how many times I see the same old mistakes,
Title Tags: Greg Boser calls it the wish list I call it the 1 out of 3 rule. Basically it's when you stick all the keywords you would like to rank for,
WeSellFlowers.com Buy Flowers, Plants online, buy flowers online
Please I wouldn't even click on that title try to structure them well for User first then search engine, it's no good ranking if you are losing 20% clicks because you title looks poor..
Buy Plants and Flowers online today from WeSellFlowers.com
Also unless you are Ebay or IBM put your brand at the rear, most people won't have heard of you before so don't waste that precision real estate,
The Homepage: this is my personal favourite the www or the NON-www pick one and stick to it and 301 the other, I saw more than one of these at SES San Jose in my site clinic, btw you are leaving Page Rank on the table and may cause dupe content issues if you site is down for any period of time, also don't link back to you home page with index.php root is fine, in the last site clinic I had the worse example
domain.com resolved Pagerank 3
www.domain.com resolved with Pagerank 5
The homepage had 2 links, www.domain.com/default .php and www.domain.com/Default.php , just keep it consistent search engines tend to get this right for you but I have seen case where they don't and it just all falls apart.
Images: Think load time people, if I have to make small talk in a site clinic becaue your site is taking so long to load (even on a crappy connection people still have those!), Think what a PPC click is going to look like I would hit the back button so fast if it’s taking an age to load. also think Quailty score issues.
Relative URl V Absolute URL : this is a no brainer for me Absolute Absolute Absolute.. just think proxies, what if a proxy hits your site at least your Absolute URL will get you a back link, if you use relative links you get dupe content.
Images that look like banners : nothing to do with Seo more to do with usability, the time that i see people stick special offer banners that look like they are affialite banners never ceases to suprise me